Methods for inhibiting B lymphocyte proliferation with soluble ztnf4 receptor

ABSTRACT

Soluble, secreted tumor necrosis factor receptor polypeptides, polynucleotides encoding the polypeptides, and related compositions and methods are disclosed. The polypeptides comprise one cysteine-rich repeat that is homologous to other tumor necrosis factor receptors, such as transmembrane activator and CAML-interactor (TACI). The polypeptides may be used for detecting ligands, agonists and antagonists. The polypeptides may also be used in methods that modulate B cell activation.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 09/569,245, filed May 11, 2000, which is a continuation-in-partof U.S. patent application Ser. No. 09/479,856, filed on Jan. 7, 2000now abandoned, which is related to Provisional Applications 60/115,068,filed on Jan. 7, 1999 and 60/169,890, filed on Dec. 9, 1999. Under 35U.S.C. §119(e)(1), this application claims benefit of said ProvisionalApplications.

BACKGROUND OF THE INVENTION

Cellular interactions which occur during an immune response areregulated by members of several families of cell surface receptors,including the tumor necrosis factor receptor (TNFR) family. The TNFRfamily consists of a number of integral membrane glycoprotein receptorsmany of which, in conjunction with their respective ligands, regulateinteractions between different hematopoietic cell lineages (Smith etal., The TNF Receptor Superfamily of Cellular and Viral Proteins:Activation, Costimulation and Death, 76:959-62, 1994; Cosman, Stem Cells12:440-55, 1994).

One such receptor is TACI, transmembrane activator and CAML-interactor(von Bülow and Bram, Science 228:138-41, 1997 and WIPO Publication WO98/39361). TACI is a membrane bound receptor having an extracellulardomain containing two cysteine-rich pseudo-repeats, a transmembranedomain and a cytoplasmic domain that interacts with CAML(calcium-modulator and cyclophilin ligand), an integral membrane proteinlocated at intracellular vesicles which is a co-inducer of NF-ATactivation when overexpressed in Jurkat cells. TACI is associated with Bcells and a subset of T cells. von Bülow and Bram (ibid.) report thatthe ligand for TACI is not known.

The polypeptides of the present invention, a TACI isoform having onlyone cysteine-rich pseudo-repeat (BR43x2), TACI and a related B cellprotein, BCMA (Gras et al., Int. Immunol. 17:1093-106, 1995) were foundto bind to the TNF ligand, ztnf4, now know as neutrokine α (WIPOPublication, WO 98/18921), BLyS (Moore et al., Science, 285:260-3,1999), BAFF (Schneider et al., J. Exp. Med. 189:1747-56, 1999), TALL-1(Shu et al., J. Leukoc. Biol. 65:680-3, 1999) or THANK (Mukhopadhyay etal., J. Biol. Chem. 274:15978-81, 1999). As such, BR43x2, TACI, and BCMAwould be useful to regulate the activity of ztnf4 in particular, theactivation of B cells.

Towards this end, the present invention provides protein therapeuticsfor modulating the activity of ztnf4 or other BR43x2, TACI or BCMAligands, related compositions and methods as well as other uses thatshould be apparent to those skilled in the art from the teachingsherein.

SUMMARY OF THE INVENTION

Within one aspect the invention provides a method of inhibiting ztnf4activity in a mammal comprising administering to said mammal an amountof a compound selected from the group consisting of: a) a soluble ztnf4receptor; b) a polypeptide comprising the extracellular domain ofBR43x2; c) a polypeptide comprising the extracellular domain of TACI; d)a polypeptide comprising the extracellular domain of BCMA; e) apolypeptide comprising the sequence of SEQ ID NO:10; f) an antibody orantibody fragment which specifically binds to a polypeptide of SEQ IDNO:2; g) an antibody or antibody fragment which specifically binds to apolypeptide of SEQ ID NO:4; h) an antibody or antibody fragment whichspecifically binds to a polypeptide of SEQ ID NO:6; i) an antibody orantibody fragment which specifically binds to a polypeptide of SEQ IDNO:8; j) an antibody or antibody fragment which specifically binds to apolypeptide of SEQ ID NO:10; k) a polypeptide of SEQ ID NO:4; l) aminoacid residues 1-166 of SEQ ID NO:6; and m) amino acid residues 1-150 ofSEQ ID NO:8. Within one embodiment the compound is a fusion proteinconsisting of a first portion and a second portion joined by a peptidebond, said first portion comprising a polypeptide selected from thegroup consisting of: a) a soluble ztnf4 receptor; b) a polypeptidecomprising the sequence of SEQ ID NO:10; c) a polypeptide comprisingamino acid residues 25-58 of SEQ ID NO:2; d) a polypeptide comprisingamino acid residues 34-66 of SEQ ID NO:6; e) a polypeptide comprisingamino acid residues 71-104 of SEQ ID NO:6; f) a polypeptide comprisingamino acid residues 25-104 of SEQ ID NO:6; g) a polypeptide comprisingamino acid residues 8-37 of SEQ ID NO:8; h) a polypeptide comprisingamino acid residues 41-88 of SEQ ID NO:8; i) a polypeptide comprisingamino acid residues 8-88 of SEQ ID NO:8; and said second portioncomprising another polypeptide. Within a related embodiment the firstportion further comprises a polypeptide selected from the groupconsisting of: a) amino acid residues 59-120 of SEQ ID NO:2; b) aminoacid residues 105-166 of SEQ ID NO:6; and c) amino acid residues 89-150of SEQ ID NO:8. Within another embodiment the first portion is selectedfrom the group consisting of: a) a polypeptide comprising theextracellular domain of BR43x2; b) a polypeptide comprising theextracellular domain of TACI; and c) a polypeptide comprising theextracellular domain of BCMA. Within another embodiment the firstportion is selected from the group consisting of: a) a polypeptide ofSEQ ID NO:4; b) amino acid residues 1-154 of SEQ ID NO:6; and c) aminoacid residues 1-48 of SEQ ID NO:8. Within a further embodiment thesecond portion is an immunoglobulin heavy chain constant region.

Within another embodiment is a method wherein said antibody or antibodyfragment is selected from the group consisting of: a) polyclonalantibody; b) murine monoclonal antibody; c) humanized antibody derivedfrom b); and d) human monoclonal antibody. Within a related embodimentthe antibody fragment is selected from the group consisting of F(ab′),F(ab), Fab′, Fab, Fv, scFv, and minimal recognition unit.

Within yet another embodiment is a method wherein said mammal is aprimate.

Within other embodiments is a method wherein said ztnf4 activity isassociated with B lymphocytes, activated B lymphocytes, or resting Blymphocytes.

Within still another embodiment is a method wherein said ztnf4 activityis associated with antibody production. Within a related embodiment theantibody production is associated with an autoimmune disease. Withinanother related embodiment the autoimmune disease is systemic lupuserythomatosis, myasthenia gravis, multiple sclerosis, insulin dependentdiabetes mellitus or rheumatoid arthritis.

Within another embodiment the ztnf4 activity is associated with asthma,bronchitis or emphysema.

Within other embodiments the ztnf4 activity is associated with end stagerenal failure or renal disease. Within a related embodiment the renaldisease is glomerulonephritis, vasculitis, chronic lymphoid leukemia,nephritis or pyelonephritis.

Within another embodiment ztnf4 activity is associated with renalneoplasms, multiple myelomas, lymphomas, light chain neuropathy oramyloidosis.

Another embodiment provides a method wherein the ztnf4 activity isassociated with effector T cells. Within a related embodiment the ztnf4activity is associated with regulating immune response. Within anotherembodiment the ztnf4 activity is associated with immunosuppression.Within yet another embodiment the immunosuppression is associated withgraft rejection, graft verses host disease or inflammation. Within stillanother embodiment the immunosuppression is associated with autoimmunedisease. Another embodiment provides that the autoimmune disease isinsulin-dependent diabetes mellitus or Crohn's disease. Still anotherembodiment provides that the immunosuppression is associated withinflammation. Within a related embodiment the inflammation is associatedwith joint pain, swelling, anemia, or septic shock.

Within another aspect the invention provides a method for inhibitingBR43x2, TACI or BCMA receptor-ligand engagement comprising administeringan amount of a compound selected from the group consisting of: a) aztnf4 receptor, b) a polypeptide comprising the extracellular domain ofBR43x2; c) a polypeptide comprising the extracellular domain of TACI; d)a polypeptide comprising the extracellular domain of BCMA; e) apolypeptide comprising the sequence of SEQ ID NO:10; f) an antibody orantibody fragment which specifically binds to a polypeptide of SEQ IDNO:2; g) an antibody or antibody fragment which specifically binds to apolypeptide of SEQ ID NO:4; h) an antibody or antibody fragment whichspecifically binds to a polypeptide of SEQ ID NO:6; i) an antibody orantibody fragment which specifically binds to a polypeptide of SEQ IDNO:8; j) an antibody or antibody fragment which specifically binds to apolypeptide of SEQ ID NO:10; k) an antibody or antibody fragment whichspecifically binds to a polypeptide of SEQ ID NO:18; l) an antibody orantibody fragment which specifically binds to a polypeptide of SEQ IDNO:20; m) a polypeptide of SEQ ID NO:4; n) amino acid residues 1-166 ofSEQ ID NO:6; and o) amino acid residues 1-150 of SEQ ID NO:8. Within oneembodiment the compound is a fusion protein consisting of a firstportion and a second portion joined by a peptide bond, said firstportion comprising a polypeptide selected from the group consisting of:a) a polypeptide comprising the sequence of SEQ ID NO:8; b) apolypeptide comprising amino acid residues 25-58 of SEQ ID NO:2; c) apolypeptide comprising amino acid residues 34-66 of SEQ ID NO:6; d) apolypeptide comprising amino acid residues 71-104 of SEQ ID NO:6; e) apolypeptide comprising amino acid residues 25-104 of SEQ ID NO:6; f) apolypeptide comprising amino acid residues 8-37 of SEQ ID NO:8; g) apolypeptide comprising amino acid residues 41-88 of SEQ ID NO:8; h) apolypeptide comprising amino acid residues 8-88 of SEQ ID NO:8; and saidsecond portion comprising another polypeptide. Within another embodimentthe first portion further comprises a polypeptide selected from thegroup consisting of: a) amino acid residues 59-120 of SEQ ID NO:2; b)amino acid residues 105-166 of SEQ ID NO:6; and c) amino acid residues89-150 of SEQ ID NO:8. Within yet another embodiment the first portionis selected from the group consisting of: a) a polypeptide comprisingthe extracellular domain of BR43x2; b) a polypeptide comprising theextracellular domain of TACI; and c) a polypeptide comprising theextracellular domain of BCMA. Within yet another embodiment the firstportion is selected from the group consisting of: a) a polypeptide ofSEQ ID NO:4; b) amino acid residues 1-154 of SEQ ID NO:6; and c) aminoacid residues 1-48 of SEQ ID NO:8. Within a related embodiment thesecond portion is an immunoglobulin heavy chain constant region.

Within another embodiment the said antibody or antibody fragment isselected from the group consisting of: a) polyclonal antibody; b) murinemonoclonal antibody; c) humanized antibody derived from b); and d) humanmonoclonal antibody. Within a related embodiment the antibody fragmentis selected from the group consisting of F(ab′), F(ab), Fab′, Fab, Fv,scFv, and minimal recognition unit.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with lymphocytes, activated B lymphocytes, orresting B lymphocytes.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with antibody production. Within a relatedembodiment the antibody production is associated with an autoimmunedisease. Within another embodiment the autoimmune disease is systemiclupus erythematosis, myasthenia gravis, insulin dependent diabetesmellitus, multiple sclerosis, or rheumatoid arthritis.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with asthma, bronchitis or emphysema.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with end stage renal failure.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with renal disease. Within a related embodimentthe renal disease is glomerulonephritis, vasculitis, nephritis, chroniclymphoid leukemia, or pyelonephritis.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with renal neoplasms, multiple myelomas,lymphomas, light chain neuropathy or amyloidosis.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with effector T cells. Within a relatedembodiment the BR43x2, TACI or BCMA receptor-ligand engagement isassociated with regulation of immune response. Within another relatedembodiment the BR43x2, TACI or BCMA receptor-ligand engagement isassociated with immunosuppression. Within another embodiment theimmunosuppression is associated with graft rejection, graft verses hostdisease or inflammation. Within another embodiment the immunosuppressionis associated with autoimmune disease. Within a related embodiment theautoimmune disease is insulin-dependent diabetes mellitus or Crohn'sDisease.

Within other embodiment the BR43x2, TACI or BCMA receptor-ligandengagement is associated with inflammation. Within a related embodimentthe inflammation is associated with joint pain, swelling, anemia, orseptic shock.

The invention also provides an isolated polynucleotide molecule encodinga polypeptide of SEQ ID NO:2. Also provided is an isolatedpolynucleotide molecule of SEQ ID NO:1.

The invention also provides an expression vector comprising thefollowing operably linked elements: a transcription promoter; apolynucleotide molecule as described above; and a transcriptionterminator.

The invention further provides a cultured cell into which has beenintroduced an expression vector as described above, wherein saidcultured cell expresses said polypeptide encoded by said polynucleotidesegment.

Also provided is a method of producing a polypeptide comprising:culturing a cell into which has been introduced an expression vector asdescribed above; whereby said cell expresses said polypeptide encoded bysaid polynucleotide molecule; and recovering said expressed polypeptide.

The invention provides an isolated polypeptide having the sequence ofSEQ ID NO:2. In a related embodiment the polypeptide is in combinationwith a pharmaceutically acceptable vehicle.

Within another aspect the invention provides a method for regulating Blymphocytes in a recipient in need of such B lymphocyte regulation,comprising administering to said recipient a pharmaceutically effectiveamount of a soluble ztnf4 receptor in a pharmaceutically acceptablevehicle. Within a related embodiment the B lymphocyte regulation isselected from the group consisting of: a) inhibition of B lymphocyteproliferation; b) inhibition of B lymphocyte activation; c) inhibitionof B lymphocyte homeostasis; and d) inhibition of B lymphocyte effectorfunction. Within another embodiment the B lymphocyte regulation ismodulation of autoantibody production. Within yet another embodiment theB lymphocyte regulation is the reduction of B lymphocytes in theperiphery of said recipient. Within one related embodiment the Blymphocytes are pre-pro or immature B lymphocytes. Within anotherembodiment the B lymphocyte regulation is associated with an autoimmunedisease. Within a related embodiment the autoimmune disease is systemiclupus erythematosis, myasthenia gravis, insulin dependent diabetesmellitus, multiple sclerosis, or rheumatoid arthritis.

Another embodiment provides a method wherein the B lymphocyte regulationis associated with asthma, bronchitis or emphysema.

Another embodiment provides a method wherein the B lymphocyte regulationis associated with end stage renal failure.

Another embodiment provides a method wherein the B lymphocyte regulationis associated with renal disease. In a related embodiment the renaldisease is glomerulonephritis, vasculitis, nephritis, chronic lymphoidleukemia, or pyelonephritis.

In yet another embodiment is provided a method wherein the B lymphocyteregulation is associated with renal neoplasms, multiple myelomas,lymphomas, light chain neuropathy or amyloidosis.

Another embodiment provides a method wherein B lymphocyte regulation isassociated with effector T cells. Within one embodiment the B lymphocyteregulation is associated with regulation of immune response. Within arelated embodiment the B lymphocyte regulation is associated withimmunosuppression. Within another related embodiment theimmunosuppression is associated with graft rejection, graft verses hostdisease or inflammation.

Within another embodiment is provided a method wherein B lymphocyteregulation is associated with autoimmune disease. Within a relatedembodiment the autoimmune disease is insulin-dependent diabetes mellitusor Crohn's Disease.

Within another embodiment the B lymphocyte regulation is associated withinflammation.

Within in another aspect the invention provides a method for reducingproteinuria in a recipient in need of such reduction, comprisingadministering to said recipient a pharmaceutically effective amount of asoluble ztnf4 receptor in a pharmaceutically acceptable vehicle. Withinone embodiment the proteinuria is stimulated by ztnf4. Within anotherembodiment the proteinuria is associated with an autoimmune disease.Within a related embodiment the autoimmune disease is systemic lupuserythomatosis, myasthenia gravis, or rheumatoid arthritis.

Within another embodiment is provided a method wherein said proteinuriais associated with end stage renal failure.

Yet another embodiment provides a method wherein the proteinuria isassociated with renal disease. A related embodiment provides that therenal disease is glomerulonephritis, vasculitis, nephritis, chroniclymphoid leukemia, or pyelonephritis.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 shows a multiple amino acid sequence alignment between BR43x2,TACI (von Büllow and Bram, ibid.) (SEQ ID NO:6), BCMA (Gras et al.,ibid.) (SEQ ID NO:8) and BR43x1 (SEQ ID NO:9). The cysteine-rich pseudorepeats and transmembrane domain are noted.

FIG. 2 shows a Scatchard plot analysis of soluble I¹²⁵-ztnf4 binding toTACI and BCMA expressed by stable BHK transfectants.

FIG. 3A shows ztnf4 co-activating human B lymphocytes to proliferate andsecrete immunoglobulin.

FIG. 3B shows levels of IgM and IgG measured in supernatants obtainedfrom B cells stimulated with soluble ztnf4 in the presence of IL4 orIL4+IL5 after 9 days in culture.

FIG. 4 shows human peripheral blood B cells stimulated with solubleztnf4 or control protein (ubiquitin) in the presence of IL-4 for 5 daysin vitro. Purified TACI-Ig, BCMA-Ig and control Fc were tested forinhibition of ztnf4 specific proliferation.

FIG. 5A shows results from ztnf4 transgenic animals that have developedcharacteristics of SLE.

FIG. 5B shows lymph node, spleen and thymus cells from ztnf4 transgenicanimals stained with antibodies to CD5, CD4 and CD8.

FIG. 5C shows total IgM, IgG and IgE levels in serum from transgenicztnf4 animals ranging from 6 to 23 weeks of age.

FIG. 5D shows effector T cells in ztnf4 transgenic mice.

FIGS. 6A and B show elevated ztnf4 levels in serum obtained from NZBWF1mice and MRL/lpr/lpr mice that correlates with development of SLE.

FIG. 7 shows the percentage of NZBWF1 mice that develop proteinurea overthe course of the study.

FIG. 8 shows anti-dsDNA levels by ELISA from ztnf4 transgenic mice andcontrol litter mates compared to serum from ZNBWF1 and MRL/lpr/lpr mice.

FIGS. 9A and 9B show the results of a collagen ELISA on serum taken fromDBA/1J mice in CIA model.

FIG. 10 shows levels of ztnf4 in SLE patients.

These and other aspects of the invention will become evident uponreference to the following detailed description.

DETAILED DESCRIPTION OF THE INVENTION

Prior to setting forth the invention, it may be helpful to anunderstanding thereof to set forth definitions of certain terms to beused hereinafter:

Affinity tag: is used herein to denote a polypeptide segment that can beattached to a second polypeptide to provide for purification ordetection of the second polypeptide or provide sites for attachment ofthe second polypeptide to a substrate. In principal, any peptide orprotein for which an antibody or other specific binding agent isavailable can be used as an affinity tag. Affinity tags include apoly-histidine tract, protein A (Nilsson et al., EMBO J. 4:1075, 1985;Nilsson et al., Methods Enzymol. 198:3, 1991), glutathione S transferase(Smith and Johnson, Gene 67:31, 1988), Glu-Glu affinity tag(Grussenmeyer et al., Proc. Natl. Acad. Sci. USA 82:7952-4, 1985),substance P, Flag™ peptide (Hopp et al., Biotechnology 6:1204-10, 1988),streptavidin binding peptide, or other antigenic epitope or bindingdomain. See, in general, Ford et al., Protein Expression andPurification 2: 95-107, 1991. DNAs encoding affinity tags are availablefrom commercial suppliers (e.g., Pharmacia Biotech, Piscataway, N.J.).

Allelic variant: Any of two or more alternative forms of a geneoccupying the same chromosomal locus. Allelic variation arises naturallythrough mutation, and may result in phenotypic polymorphism withinpopulations. Gene mutations can be silent (i.e., no change in theencoded polypeptide), or may encode polypeptides having altered aminoacid sequence. The term “allelic variant” is also used herein to denotea protein encoded by an allelic variant of a gene. Also included are thesame protein from the same species which differs from a reference aminoacid sequence due to allelic variation. Allelic variation refers tonaturally occurring differences among individuals in genes encoding agiven protein.

Amino-terminal and carboxyl-terminal: are used herein to denotepositions within polypeptides and proteins. Where the context allows,these terms are used with reference to a particular sequence or portionof a polypeptide or protein to denote proximity or relative position.For example, a certain sequence positioned carboxyl-terminal to areference sequence within a protein is located proximal to the carboxylterminus of the reference sequence, but is not necessarily at thecarboxyl terminus of the complete protein.

Complement/anti-complement pair: Denotes non-identical moieties thatform a non-covalently associated, stable pair under appropriateconditions. For instance, biotin and avidin (or streptavidin) areprototypical members of a complement/anti-complement pair. Otherexemplary complement/anti-complement pairs include receptor/ligandpairs, antibody/antigen (or hapten or epitope) pairs, sense/antisensepolynucleotide pairs, and the like. Where subsequent dissociation of thecomplement/anti-complement pair is desirable, thecomplement/anti-complement pair preferably has a binding affinity of<10⁻⁹ M.

Contig: Denotes a polynucleotide that has a contiguous stretch ofidentical or complementary sequence to another polynucleotide.Contiguous sequences are said to “overlap” a given stretch ofpolynucleotide sequence either in their entirety or along a partialstretch of the polynucleotide. For example, representative contigs tothe polynucleotide sequence 5′-ATGGCTTAGCTT-3′ are 5′-TAGCTTgagtct-3′and 3′-gtcgacTACCGA-5′.

Complements of polynucleotide molecules: Denotes polynucleotidemolecules having a complementary base sequence and reverse orientationas compared to a reference sequence. For example, the sequence 5′ATGCACGGG 3′ is complementary to 5′ CCCGTGCAT 3′.

Degenerate Nucleotide Sequence or Degenerate Sequence: Denotes asequence of nucleotides that includes one or more degenerate codons (ascompared to a reference polynucleotide molecule that encodes apolypeptide). Degenerate codons contain different triplets ofnucleotides, but encode the same amino acid residue (i.e., GAU and GACtriplets each encode Asp).

Expression vector: A DNA molecule, linear or circular, that comprises asegment encoding a polypeptide of interest operably linked to additionalsegments that provide for its transcription. Such additional segmentsmay include promoter and terminator sequences, and optionally one ormore origins of replication, one or more selectable markers, anenhancer, a polyadenylation signal, and the like. Expression vectors aregenerally derived from plasmid or viral DNA, or may contain elements ofboth.

Isoform: refers to different forms of a protein that may be producedfrom different genes or from the same gene by alternate splicing. Insome cases, isoforms differ in their transport activity, time ofexpression in development, tissue distribution, location in the cell ora combination of these properties.

Isolated polynucleotide: denotes that the polynucleotide has beenremoved from its natural genetic milieu and is thus free of otherextraneous or unwanted coding sequences, and is in a form suitable foruse within genetically engineered protein production systems. Suchisolated molecules are those that are separated from their naturalenvironment and include cDNA and genomic clones. Isolated DNA moleculesof the present invention are free of other genes with which they areordinarily associated, but may include naturally occurring 5′ and 3′untranslated regions such as promoters and terminators. Theidentification of associated regions will be evident to one of ordinaryskill in the art (see for example, Dynan and Tijan, Nature 316:774-78,1985).

Isolated polypeptide or protein: is a polypeptide or protein that isfound in a condition other than its native environment, such as apartfrom blood and animal tissue. In a preferred form, the isolatedpolypeptide is substantially free of other polypeptides, particularlyother polypeptides of animal origin. It is preferred to provide thepolypeptides in a highly purified form, i.e. greater than 95% pure, morepreferably greater than 99% pure. When used in this context, the term“isolated” does not exclude the presence of the same polypeptide inalternative physical forms, such as dimers or alternatively glycosylatedor derivatized forms.

Operably linked: As applied to nucleotide segments, the term “operablylinked” indicates that the segments are arranged so that they functionin concert for their intended purposes, e.g., transcription initiates inthe promoter and proceeds through the coding segment to the terminator.

Ortholog: Denotes a polypeptide or protein obtained from one speciesthat is the functional counterpart of a polypeptide or protein from adifferent species. Sequence differences among orthologs are the resultof speciation.

Polynucleotide: denotes a single- or double-stranded polymer ofdeoxyribonucleotide or ribonucleotide bases read from the 5′ to the 3′end. Polynucleotides include RNA and DNA, and may be isolated fromnatural sources, synthesized in vitro, or prepared from a combination ofnatural and synthetic molecules. Sizes of polynucleotides are expressedas base pairs (abbreviated “bp”), nucleotides (“nt”), or kilobases(“kb”). Where the context allows, the latter two terms may describepolynucleotides that are single-stranded or double-stranded. When theterm is applied to double-stranded molecules it is used to denoteoverall length and will be understood to be equivalent to the term “basepairs”. It will be recognized by those skilled in the art that the twostrands of a double-stranded polynucleotide may differ slightly inlength and that the ends thereof may be staggered as a result ofenzymatic cleavage; thus all nucleotides within a double-strandedpolynucleotide molecule may not be paired. Such unpaired ends will ingeneral not exceed 20 nt in length.

Polypeptide: Is a polymer of amino acid residues joined by peptidebonds, whether produced naturally or synthetically. Polypeptides of lessthan about 10 amino acid residues are commonly referred to as“peptides”.

Promoter: Denotes a portion of a gene containing DNA sequences thatprovide for the binding of RNA polymerase and initiation oftranscription. Promoter sequences are commonly, but not always, found inthe 5′ non-coding regions of genes.

Protein: is a macromolecule comprising one or more polypeptide chains. Aprotein may also comprise non-peptidic components, such as carbohydrategroups. Carbohydrates and other non-peptidic substituents may be addedto a protein by the cell in which the protein is produced, and will varywith the type of cell. Proteins are defined herein in terms of theiramino acid backbone structures; substituents such as carbohydrate groupsare generally not specified, but may be present nonetheless.

Receptor: A cell-associated protein, or a polypeptide subunit of suchprotein, that binds to a bioactive molecule (the “ligand”) and mediatesthe effect of the ligand on the cell. Binding of ligand to receptorresults in a change in the receptor (and, in some cases, receptormultimerization, i.e., association of identical or different receptorsubunits) that causes interactions between the effector domain(s) of thereceptor and other molecule(s) in the cell. These interactions in turnlead to alterations in the metabolism of the cell. Metabolic events thatare linked to receptor-ligand interactions include gene transcription,phosphorylation, dephosphorylation, cell proliferation, increases incyclic AMP production, mobilization of cellular calcium, mobilization ofmembrane lipids, cell adhesion, hydrolysis of inositol lipids andhydrolysis of phospholipids. BR43x2 has characteristics of TNFreceptors, as discussed in more detail herein.

Secretory signal sequence: A DNA sequence that encodes a polypeptide (a“secretory peptide”) that, as a component of a larger polypeptide,directs the larger polypeptide through a secretory pathway of a cell inwhich it is synthesized. The larger polypeptide is commonly cleaved toremove the secretory peptide during transit through the secretorypathway.

Soluble receptor: A receptor polypeptide that is not bound to a cellmembrane. Soluble receptors are most commonly ligand-binding receptorpolypeptides that lack transmembrane and cytoplasmic domains. Solublereceptors can comprise additional amino acid residues, such as affinitytags that provide for purification of the polypeptide or provide sitesfor attachment of the polypeptide to a substrate. Many cell-surfacereceptors have naturally occurring, soluble counterparts that areproduced by proteolysis or translated from alternatively spliced mRNAs.Receptor polypeptides are said to be substantially free of transmembraneand intracellular polypeptide segments when they lack sufficientportions of these segments to provide membrane anchoring or signaltransduction, respectively.

Molecular weights and lengths of polymers determined by impreciseanalytical methods (e.g., gel electrophoresis) will be understood to beapproximate values. When such a value is expressed as “about” X or“approximately” X, the stated value of X will be understood to beaccurate to ±10%.

All references cited herein are incorporated by reference in theirentirety.

The present invention is based in part upon the discovery of a 1192 byDNA sequence (SEQ ID NO:1) and corresponding polypeptide sequence (SEQID NO:2) which is an isoform of the receptor TACI. The isoform has beendesignated BR43x2. A soluble form of BR43x2 is disclosed in SEQ ID NO:4,the polynucleotide encoding the soluble receptor in SEQ ID NO:3. As isdescribed in more detail herein, the BR43x2 receptor-encodingpolynucleotides and polypeptides of the present invention were initiallyidentified by signal trap cloning using a human RPMI 1788 library andthe N- or C-terminally FLAG-tagged, biotin- or FITC-labeled tumornecrosis factor ligand ztnf4, now known as neutrokine α (WIPOWO98/18921), BLyS (Moore et al., ibid.), BAFF (Schneider et al., ibid.),TALL-1 (Shu et al., ibid.) or THANK (Mukhopadhyay et al., ibid.).Positive pools were identified by ligand binding, broken down to singleclones, the cDNA isolated and sequenced. A comparison of the BR43x2deduced amino acid sequence (as represented in SEQ ID NO:2) with knowntumor necrosis factor receptors indicated that BR43x2 is an isoform ofTACI, having a single, poorly conserved, cysteine-rich pseudo-repeat.

Structurally, the TNF receptor family is characterized by anextracellular portion composed of several modules called, historically,“cysteine-rich pseudo-repeats”. A prototypical TNFR family member hasfour of these pseudo-repeats, each about 29-43 residues long, one rightafter the other. A typical pseudo-repeat has 6 cysteine residues. Theyare called pseudo-repeats because, although they appear to originatefrom a common ancestral module, they do not repeat exactly:pseudo-repeats #1, #2, #3 and #4 have characteristic sequence featureswhich distinguish them from one another. The crystal structure of thep55 TNF receptor revealed that each pseudo-repeat corresponds to onefolding domain, and that all four pseudo-repeats fold into the sametertiary structure, held together internally by disulfide bonds.

TACI contains two cysteine-rich pseudo-repeats (von Bülow and Bram,ibid.), the first is conserved in structure with other members of theTNF receptor family, the second is less conserved. The BR43x2 isoform ofthe present invention lacks the first TACI cysteine-rich pseudo-repeat,retaining only the second, less conserved repeat.

Sequence analysis of a deduced amino acid sequence of BR43x2 asrepresented in SEQ ID NO:2 indicates the presence of a mature proteinhaving an extracellular domain (residues 1-120 of SEQ ID NO:2) whichcontains one cysteine-rich pseudo-repeat (residues 25-58 of SEQ IDNO:2), a transmembrane domain (residues 121-133 of SEQ ID NO:2) and acytoplasmic domain (residues 134-247 of SEQ ID NO:2). The cysteine-richpseudo-repeat of BR43x2 has 6 conserved cysteine residues (residues 25,40, 43, 47, 54 and 58 of SEQ ID NO:2), a conserved aspartic acid residue(residue 34 of SEQ ID NO:2) and two conserved leucine residues (residues36 and 37 of SEQ ID NO:2) and shares 46% identity with the firstcysteine-rich pseudo-repeat of TACI (SEQ ID NO:6) and 35% identity withthe cysteine-rich pseudo-repeat of BCMA (SEQ ID NO:8) (FIG. 1). Thecysteine-rich pseudo-repeat can be represented by the following motif:

CX[QEK][QEKNRDHS][QE]X{0-2}[YFW][YFW]DXLLX{2}C[IMLV]XCX{3}CX{6-8}CX{2}[YF]C(SEQ ID NO:10),

wherein C represents the amino acid residue cysteine, Q glutamine, Eglutamic acid, K lysine, N asparagine, R arginine, D aspartic acid, Hhistidine, S serine, Y tyrosine, F phenylalanine, W tryptophan, Lleucine, I isoleucine, V valine and X represents any naturally occurringamino acid residue except cysteine. Amino acid residues in squarebrackets “[ ]” indicate the allowed amino acid residue variation at thatposition. The number in the braces “{ }” indicates the number of allowedamino acid residues at that position.

The present invention also provides soluble polypeptides of from 32 to40 amino acid residues in length as provided by SEQ ID NO:10.

The soluble BR43x2 receptor, as represented by residues 1-120 of SEQ IDNO:4, contains one cysteine-rich pseudo-repeat (residues 25-58 of SEQ IDNO:4) and lacks the transmembrane and cytoplasmic domains of BR43x2 asdescribed in SEQ ID NO:2.

Those skilled in the art will recognize that these domain boundaries areapproximate, and are based on alignments with known proteins andpredictions of protein folding. These features indicate that thereceptor encoded by the DNA sequences of SEQ ID NOs:1 and 3 is a memberof the TNF receptor family.

Northern blot and Dot blot analysis of the tissue distribution of themRNA corresponding to nucleotide probes to BR43x1 which are predicted todetect BR43x2 expression showed expression in spleen, lymph node, CD19+cells, weakly in mixed lymphocyte reaction cells, Daudi and Raji cells.Using reverse transcriptase PCR BR43x1 was detected in B cells only andnot in activated T cells as had been reported for TACI (von Büllow andBram, ibid.). Using a BR43x2 probe that overlaps 100% with thecorresponding TACI sequence, TACI and BR43x2 were detected in spleen,lymph node and small intestine, stomach, salivary gland, appendix, lung,bone marrow, fetal spleen, CD 19⁺ cells, and Raji cells.

Using Northern Blot analysis BCMA was detected in small intestine,spleen, stomach, colon, appendix, lymph node, trachea, and testis. BCMAwas also detected in adenolymphoma, non-Hodgkins lymphoma, and parotidtumor, detected faintly in CD 8⁺, CD 19⁺, MLR cells, Daudi, Raji and Hut78 cells.

Northern blot analysis was also done using murine ztnf4 (SEQ ID NO:19)and like human TACI, BCMA, and BR43x2, murine ztnf4 expression wasdetected predominately in spleen and thymus. Murine ztnf4 was alsoexpressed in lung and faint expression was detected in skin and heart.

Additional blot analysis is described in the Examples herein.

The present invention also provides polynucleotide molecules, includingDNA and RNA molecules, that encode the BR43x2 polypeptides disclosedherein. Those skilled in the art will readily recognize that, in view ofthe degeneracy of the genetic code, considerable sequence variation ispossible among these polynucleotide molecules. SEQ ID NO:11 is adegenerate DNA sequence that encompasses all DNAs that encode thesoluble BR43x2 polypeptide of SEQ ID NO:4. Similarly, SEQ ID NO:12 is adegenerate DNA sequence that encompasses all DNAs that encode the BR43x2polypeptide of SEQ ID NO:2. Those skilled in the art will recognize thatthe degenerate sequence of SEQ ID NO:12 also provides all RNA sequencesencoding SEQ ID NO:4 by substituting U for T. Thus, BR43x2polypeptide-encoding polynucleotides comprising nucleotide 1 tonucleotide 360 of SEQ ID NO:11, nucleotide 1 to 741 of SEQ ID NO:12 andtheir RNA equivalents are contemplated by the present invention. Table 1sets forth the one-letter codes used within SEQ ID NOs:11 and 12 todenote degenerate nucleotide positions. “Resolutions” are thenucleotides denoted by a code letter. “Complement” indicates the codefor the complementary nucleotide(s). For example, the code Y denoteseither C or T, and its complement R denotes A or G, A beingcomplementary to T, and G being complementary to C.

TABLE 1 Nucleotide Resolution  Complement Resolution A A T T C C G G G GC C T T A A R A|G Y C|T Y C|T R A|G M A|C K G|T K G|T M A|C S C|G S C|GW A|T W A|T H A|C|T D A|G|T B C|G|T V A|C|G V A|C|G B C|G|T D A|G|T HA|C|T N A|C|G|T N A|C|G|T

The degenerate codons used in SEQ ID NOs:11 and 12, encompassing allpossible codons for a given amino acid, are set forth in Table 2.

TABLE 2 One Amino  Letter Degenerate Acid Code Codons Codon Cys CTGC TGT TGY Ser S AGC AGT TCA TCC TCG TCT WSN Thr T ACA ACC ACG ACT ACNPro P CCA CCC CCG CCT CCN Ala A GCA GCC GCG GCT GCN Gly GGGA GGC GGG GGT GGN Asn N AAC AAT AAY Asp D GAC GAT GAY Glu E GAA GAGGAR Gln Q CAA CAG CAR His H CAC CAT CAY Arg R AGA AGG CGA CGC CGG CGTMGN Lys K AAA AAG AAR Met M ATG ATG Ile I ATA ATC ATT ATH Leu LCTA CTC CTG CTT TTA TTG YTN Val V GTA GTC GTG GTT GTN Phe F TTC TTT TTYTyr Y TAC TAT TAY Trp W TGG TGG Ter . TAA TAG TGA TRR Asn|Asp B RAYGlu|Gln Z SAR Any X NNN

One of ordinary skill in the art will appreciate that some ambiguity isintroduced in determining a degenerate codon, representative of allpossible codons encoding each amino acid. For example, the degeneratecodon for serine (WSN) can, in some circumstances, encode arginine(AGR), and the degenerate codon for arginine (MGN) can, in somecircumstances, encode serine (AGY). A similar relationship existsbetween codons encoding phenylalanine and leucine. Thus, somepolynucleotides encompassed by the degenerate sequence may encodevariant amino acid sequences, but one of ordinary skill in the art caneasily identify such variant sequences by reference to the amino acidsequences of SEQ ID NOs:2 and 4. Variant sequences can be readily testedfor functionality as described herein.

One of ordinary skill in the art will also appreciate that differentspecies can exhibit “preferential codon usage.” In general, see,Grantham, et al., Nuc. Acids Res. 8:1893-912, 1980; Haas, et al. Curr.Biol. 6:315-24, 1996; Wain-Hobson, et al., Gene 13:355-64, 1981;Grosjean and Fiers, Gene 18:199-209, 1982; Holm, Nuc. Acids Res.14:3075-87, 1986; Ikemura, J. Mol. Biol. 158:573-97, 1982. As usedherein, the term “preferential codon usage” or “preferential codons” isa term of art referring to protein translation codons that are mostfrequently used in cells of a certain species, thus favoring one or afew representatives of the possible codons encoding each amino acid (SeeTable 2). For example, the amino acid threonine (Thr) may be encoded byACA, ACC, ACG, or ACT, but in mammalian cells ACC is the most commonlyused codon; in other species, for example, insect cells, yeast, virusesor bacteria, different Thr codons may be preferential. Preferentialcodons for a particular species can be introduced into thepolynucleotides of the present invention by a variety of methods knownin the art. Introduction of preferential codon sequences intorecombinant DNA can, for example, enhance production of the protein bymaking protein translation more efficient within a particular cell typeor species. Therefore, the degenerate codon sequences disclosed in SEQID NOs:11 and 12 serve as a template for optimizing expression ofpolynucleotides in various cell types and species commonly used in theart and disclosed herein. Sequences containing preferential codons canbe tested and optimized for expression in various species, and testedfor functionality as disclosed herein.

The highly conserved amino acids in the cysteine-rich pseudo-repeat ofBR43x2 can be used as a tool to identify new family members. Forinstance, reverse transcription-polymerase chain reaction (RT-PCR) canbe used to amplify sequences encoding the extracellular ligand-bindingdomain, described above, from RNA obtained from a variety of tissuesources or cell lines. In particular, highly degenerate primers designedfrom the BR43x2 sequences are useful for this purpose.

Within preferred embodiments of the invention, isolated polynucleotideswill hybridize to similar sized regions of SEQ ID NO:3, or to a sequencecomplementary thereto, under stringent conditions. In general, stringentconditions are selected to be about 5° C. lower than the thermal meltingpoint (T_(m)) for the specific sequence at a defined ionic strength andpH. The T_(m) is the temperature (under defined ionic strength and pH)at which 50% of the target sequence hybridizes to a perfectly matchedprobe. Typical stringent conditions are those in which the saltconcentration is up to about 0.03 M at pH 7 and the temperature is atleast about 60° C.

As previously noted, the isolated polynucleotides of the presentinvention include DNA and RNA. Methods for isolating DNA and RNA arewell known in the art. It is generally preferred to isolate RNA fromRPMI 1788 cells, PBMNCs, resting or activated transfected B cells ortonsil tissue, although DNA can also be prepared using RNA from othertissues or isolated as genomic DNA. Total RNA can be prepared usingguanidine HCl extraction followed by isolation by centrifugation in aCsCl gradient (Chirgwin et al., Biochemistry 18:52-94, 1979). Poly (A)⁺RNA is prepared from total RNA using the method of Aviv and Leder (Proc.Natl. Acad. Sci. USA 69:1408-12, 1972). Complementary DNA (cDNA) isprepared from poly(A)⁺ RNA using known methods. Polynucleotides encodingBR43x2 polypeptides are then identified and isolated by, for example,hybridization or PCR.

Those skilled in the art will recognize that the sequences disclosed inSEQ ID NOs:1 and 3 represent a single allele of the human gene, and thatallelic variation and alternative splicing is expected to occur. Allelicvariants of the DNA sequences shown in SEQ ID NOs:1 and 3, includingthose containing silent mutations and those in which mutations result inamino acid sequence changes, are within the scope of the presentinvention, as are proteins which are allelic variants of SEQ ID NOs:2and 4. Allelic variants and splice variants of these sequences can becloned by probing cDNA or genomic libraries from different individualsor tissues according to standard procedures known in the art.

The present invention also provides isolated BR43x2 polypeptides thatare substantially homologous to the polypeptides of SEQ ID NOs:2 and 4and their species orthologs. The term “substantially homologous” is usedherein to denote polypeptides having 50%, preferably 60%, morepreferably at least 80%, sequence identity to the sequences shown in SEQID NOs:2 and 4 or their orthologs. Such polypeptides will morepreferably be at least 90% identical, and most preferably 95% or moreidentical to SEQ ID NO:2 or its orthologs. Percent sequence identity isdetermined by conventional methods. See, for example, Altschul et al.,Bull. Math. Bio. 48: 603-66, 1986 and Henikoff and Henikoff, Proc. Natl.Acad. Sci. USA 89:10915-9, 1992. Briefly, two amino acid sequences arealigned to optimize the alignment scores using a gap opening penalty of10, a gap extension penalty of 1, and the “blosum 62” scoring matrix ofHenikoff and Henikoff (ibid.) as shown in Table 3 (amino acids areindicated by the standard one-letter codes). The percent identity isthen calculated as:

$\frac{{Total}\mspace{14mu}{number}\mspace{14mu}{of}{\mspace{11mu}\;}{identical}\mspace{14mu}{matches}}{\begin{matrix}\lbrack {{length}\mspace{14mu}{of}{\mspace{11mu}\;}{the}\mspace{14mu}{longer}\mspace{14mu}{sequence}\mspace{14mu}{plus}\mspace{14mu}{the}}  \\{{number}\mspace{14mu}{of}\mspace{14mu}{gaps}{\mspace{11mu}\;}{introduced}\mspace{14mu}{into}\mspace{14mu}{the}\mspace{14mu}{longer}} \\ {{sequence}\mspace{14mu}{in}\mspace{14mu}{order}{\mspace{11mu}\;}{to}\mspace{14mu}{align}\mspace{14mu}{the}\mspace{14mu}{two}\mspace{14mu}{sequences}} \rbrack\end{matrix}} \times 100$

TABLE 3 A R N D C Q E G H I L K M F P S T W Y V A  4 R −1  5 N −2  0  6D −2 −2  1  6 C  0 −3 −3 −3  9 Q −1  1  0  0 −3  5 E −1  0  0  2 −4  2 5 G  0 −2  0 −1 −3 −2 −2  6 H −2  0  1 −1 −3  0  0 −2  8 I −1 −3 −3 −3−1 −3 −3 −4 −3  4 L −1 −2 −3 −4 −1 −2 −3 −4 −3  2  4 K −1  2  0 −1 −3  1 1 −2 −1 −3 −2  5 M −1 −1 −2 −3 −1  0 −2 −3 −2  1  2 −1  5 F −2 −3 −3 −3−2 −3 −3 −3 −1  0  0 −3  0  6 P −1 −2 −2 −1 −3 −1 −1 −2 −2 −3 −3 −1 −2−4  7 S  1 −1  1  0 −1  0  0  0 −1 −2 −2  0 −1 −2 −1  4 T  0 −1  0 −1 −1−1 −1 −2 −2 −1 −1 −1 −1 −2 −1  1  5 W −3 −3 −4 −4 −2 −2 −3 −2 −2 −3 −2−3 −1  1 −4 −3 −2 11 Y −2 −2 −2 −3 −2 −1 −2 −3  2 −1 −1 −2 −1  3 −3 −2−2  2  7 V  0 −3 −3 −3 −1 −2 −2 −3 −3  3  1 −2  1 −1 −2 −2  0 −3 −1 4Sequence identity of polynucleotide molecules is determined by similarmethods using a ratio as disclosed above.

Substantially homologous proteins and polypeptides are characterized ashaving one or more amino acid substitutions, deletions or additions.These changes are preferably of a minor nature, that is conservativeamino acid substitutions (see Table 4) and other substitutions that donot significantly affect the folding or activity of the protein orpolypeptide; small deletions, typically of one to about 30 amino acids;and small amino- or carboxyl-terminal extensions, such as anamino-terminal methionine residue, a small linker peptide of up to about20-25 residues, or an affinity tag. Polypeptides comprising affinitytags can further comprise a proteolytic cleavage site between the BR43x2polypeptide and the affinity tag. Preferred such sites include thrombincleavage sites and factor Xa cleavage sites.

TABLE 4 Conservative amino acid substitutions Basic: arginine lysinehistidine Acidic: glutamic acid aspartic acid Polar: glutamineasparagine Hydrophobic: leucine isoleucine valine Aromatic:phenylalanine tryptophan tyrosine Small: glycine alanine serinethreonine methionine

In addition to the 20 standard amino acids, non-standard amino acids(such as 4-hydroxyproline, 6-N-methyl lysine, 2-aminoisobutyric acid,isovaline and a-methyl serine) may be substituted for amino acidresidues of BR43x2 polypeptides of the present invention. A limitednumber of non-conservative amino acids, amino acids that are not encodedby the genetic code, and unnatural amino acids may be substituted forBR43x2 polypeptide amino acid residues. The proteins of the presentinvention can also comprise non-naturally occurring amino acid residues.

Non-naturally occurring amino acids include, without limitation,trans-3-methylproline, 2,4-methanoproline, cis-4-hydroxyproline,trans-4-hydroxy-proline, N-methylglycine, allo-threonine,methylthreonine, hydroxy-ethylcysteine, hydroxyethyl-homocysteine,nitro-glutamine, homoglutamine, pipecolic acid, tert-leucine, norvaline,2-azaphenylalanine, 3-aza-phenylalanine, 4-azaphenylalanine, and4-fluoro-phenylalanine. Several methods are known in the art forincorporating non-naturally occurring amino acid residues into proteins.For example, an in vitro system can be employed wherein nonsensemutations are suppressed using chemically aminoacylated suppressortRNAs. Methods for synthesizing amino acids and aminoacylating tRNA areknown in the art. Transcription and translation of plasmids containingnonsense mutations is carried out in a cell free system comprising an E.coli S30 extract and commercially available enzymes and other reagents.Proteins are purified by chromatography. See, for example, Robertson etal., J. Am. Chem. Soc. 113:2722, 1991; Ellman et al., Methods Enzymol.202:301, 1991; Chung et al., Science 259:806-9, 1993; and Chung et al.,Proc. Natl. Acad. Sci. USA 90:10145-9, 1993). In a second method,translation is carried out in Xenopus oocytes by microinjection ofmutated mRNA and chemically aminoacylated suppressor tRNAs (Turcatti etal., J. Biol. Chem. 271:19991-8, 1996). Within a third method, E. colicells are cultured in the absence of a natural amino acid that is to bereplaced (e.g., phenylalanine) and in the presence of the desirednon-naturally occurring amino acid(s) (e.g., 2-azaphenylalanine,3-azaphenylalanine, 4-azaphenylalanine, or 4-fluoro-phenylalanine). Thenon-naturally occurring amino acid is incorporated into the protein inplace of its natural counterpart. See, Koide et al., Biochem. 33:7470-6,1994. Naturally occurring amino acid residues can be converted tonon-naturally occurring species by in vitro chemical modification.Chemical modification can be combined with site-directed mutagenesis tofurther expand the range of substitutions (Wynn and Richards, ProteinSci. 2:395-403, 1993).

A limited number of non-conservative amino acids, amino acids that arenot encoded by the genetic code, non-naturally occurring amino acids,and unnatural amino acids may be substituted for BR43x2 amino acidresidues.

Essential amino acids in the BR43x2 polypeptides of the presentinvention can be identified according to procedures known in the art,such as site-directed mutagenesis or alanine-scanning mutagenesis(Cunningham and Wells, Science 244:1081-5, 1989). Single alaninemutations are introduced at every residue in the molecule, and theresultant mutant molecules are tested for biological activity (e.g.,providing a decrease in B cell response during the immune response,inhibition or decrease in autoantibody production) to identify aminoacid residues that are critical to the activity of the molecule. Seealso, Hilton et al., J. Biol. Chem. 271:4699-708, 1996. Sites ofbiological interaction, ligand binding portions such as thecysteine-rich pseudo-repeats, can also be determined by physicalanalysis of structure, as determined by such techniques as nuclearmagnetic resonance, crystallography, electron diffraction orphotoaffinity labeling, in conjunction with mutation of putative contactsite amino acids. See, for example, de Vos et al., Science 255:306-12,1992; Smith et al., J. Mol. Biol. 224:899-904, 1992; Wlodaver et al.,FEBS Lett. 309:59-64, 1992. The identities of essential amino acids canalso be inferred from analysis of homologies with related TNFR familymembers such as TACI and BCMA.

Additional amino acid substitutions can be made within the cysteine-richpseudo-repeat of BR43x2 so long as the conserved cysteine, aspartic acidand leucine residues are retained and the higher order structure is notdisturbed. It is preferred to make substitutions within thecysteine-rich pseudo-repeat of BR43x2 by reference to the sequences ofother cysteine-rich pseudo-repeats. SEQ ID NO:10 is a generalizedcysteine-rich pseudo-repeat that shows allowable amino acidsubstitutions based on such an alignment. Substitutions with in thisdomain are subject to the limitations set forth herein.

Multiple amino acid substitutions can be made and tested using knownmethods of mutagenesis and screening, such as those disclosed byReidhaar-Olson and Sauer (Science 241:53-7, 1988) or Bowie and Sauer(Proc. Natl. Acad. Sci. USA 86:2152-6, 1989). Briefly, these authorsdisclose methods for simultaneously randomizing two or more positions ina polypeptide, selecting for functional polypeptide, and then sequencingthe mutagenized polypeptides to determine the spectrum of allowablesubstitutions at each position. Other methods that can be used includephage display (e.g., Lowman et al., Biochem. 30:10832-7, 1991; Ladner etal., U.S. Pat. No. 5,223,409; Huse, WIPO Publication WO 92/06204) andregion-directed mutagenesis (Derbyshire et al., Gene 46:145, 1986; Neret al., DNA 7:127, 1988).

Variants of the disclosed BR43x2 DNA and polypeptide sequences can begenerated through DNA shuffling as disclosed by Stemmer, Nature370:389-91, 1994, Stemmer, Proc. Natl. Acad. Sci. USA 91:10747-51, 1994and WIPO Publication WO 97/20078. Briefly, variant DNAs are generated byin vitro homologous recombination by random fragmentation of a parentDNA followed by reassembly using PCR, resulting in randomly introducedpoint mutations. This technique can be modified by using a family ofparent DNAs, such as allelic variants or DNAs from different species, tointroduce additional variability into the process. Selection orscreening for the desired activity, followed by additional iterations ofmutagenesis and assay provides for rapid “evolution” of sequences byselecting for desirable mutations while simultaneously selecting againstdetrimental changes.

Mutagenesis methods as disclosed above can be combined withhigh-throughput, automated screening methods to detect activity ofcloned, mutagenized polypeptides in host cells. Mutagenized DNAmolecules that encode active polypeptides (e.g., providing a decrease inB cell response during the immune response, inhibition or decrease inautoantibody production) can be recovered from the host cells andrapidly sequenced using modern equipment. These methods allow the rapiddetermination of the importance of individual amino acid residues in apolypeptide of interest, and can be applied to polypeptides of unknownstructure.

Using the methods discussed above, one of ordinary skill in the art canidentify and/or prepare a variety of polypeptides that are substantiallyhomologous to residues 1 to 120 of SEQ ID NO:2 or allelic variantsthereof and retain the B cell suppression properties of the wild-typeprotein. Such polypeptides may include additional amino acids or domainsfrom other members of the tumor necrosis factor receptor superfamily,affinity tags or the like. BR43x2 polypeptide or fusion constructs,containing functional domains of other members of the TNFR superfamily,constitute hybrid tumor necrosis factor receptors exhibiting modified Bcell suppression capabilities.

The present invention further provides counterpart receptors andpolynucleotides from other species (orthologs). These species include,but are not limited to mammalian, avian, amphibian, reptile, fish,insect and other vertebrate and invertebrate species. Of particularinterest are BR43x2 receptors from other mammalian species, includingmurine, porcine, ovine, bovine, canine, feline, equine, and otherprimate receptors. Orthologs of the human BR43x2 receptor can be clonedusing information and compositions provided by the present invention incombination with conventional cloning techniques. For example, a cDNAcan be cloned using mRNA obtained from a tissue or cell type thatexpresses the receptor. Suitable sources of mRNA can be identified byprobing Northern blots with probes designed from the sequences disclosedherein. A library is then prepared from mRNA of a positive tissue orcell line. A receptor-encoding cDNA can then be isolated by a variety ofmethods, such as by probing with a complete or partial human cDNA orwith one or more sets of degenerate probes based on the disclosedsequence. A cDNA can also be cloned using PCR, using primers designedfrom the sequences disclosed herein. Within an additional method, thecDNA library can be used to transform or transfect host cells, andexpression of the cDNA of interest can be detected with an antibody tothe receptor. Similar techniques can also be applied to the isolation ofgenomic clones.

The receptor polypeptides of the present invention, includingfull-length receptor polypeptides, soluble receptors polypeptides,polypeptide fragments, and fusion polypeptides, can be produced ingenetically engineered host cells according to conventional techniques.Suitable host cells are those cell types that can be transformed ortransfected with exogenous DNA and grown in culture, and includebacteria, fungal cells, and cultured higher eukaryotic cells. Eukaryoticcells, particularly cultured cells of multicellular organisms, arepreferred. Techniques for manipulating cloned DNA molecules andintroducing exogenous DNA into a variety of host cells are disclosed bySambrook et al., Molecular Cloning: A Laboratory Manual, Second Edition,Cold Spring Harbor, N.Y., 1989; and Ausubel et al., eds., CurrentProtocols in Molecular Biology, John Wiley and Sons, Inc., NY, 1987.

In general, a DNA sequence encoding a BR43x2 polypeptide is operablylinked to other genetic elements required for its expression, generallyincluding a transcription promoter and terminator, within an expressionvector. The vector will also commonly contain one or more selectablemarkers and one or more origins of replication, although those skilledin the art will recognize that within certain systems selectable markersmay be provided on separate vectors, and replication of the exogenousDNA may be provided by integration into the host cell genome. Selectionof promoters, terminators, selectable markers, vectors and otherelements is a matter of routine design within the level of ordinaryskill in the art. Many such elements are described in the literature andare available through commercial suppliers.

To direct a BR43x2 polypeptide into the secretory pathway of a hostcell, a secretory signal sequence (also known as a signal sequence,leader sequence, prepro sequence or pre sequence) is provided in theexpression vector. The secretory signal sequence may be that of theBR43x2 polypeptide, or may be derived from another secreted protein(e.g., t-PA) or synthesized de novo. The secretory signal sequence isjoined to the BR43x2 DNA sequence in the correct reading frame andpositioned to direct the newly synthesized polypeptide into thesecretory pathway of the host cell. Secretory signal sequences arecommonly positioned 5′ to the DNA sequence encoding the polypeptide ofinterest, although certain signal sequences may be positioned elsewherein the DNA sequence of interest (see, e.g., Welch et al., U.S. Pat. No.5,037,743; Holland et al., U.S. Pat. No. 5,143,830).

Cultured mammalian cells are suitable hosts within the presentinvention. Methods for introducing exogenous DNA into mammalian hostcells include calcium phosphate-mediated transfection (Wigler et al.,Cell 14:725, 1978; Corsaro and Pearson, Somatic Cell Genetics 7:603,1981; Graham and Van der Eb, Virology 52:456, 1973), electroporation(Neumann et al., EMBO J. 1:841-45, 1982), DEAE-dextran mediatedtransfection (Ausubel et al., ibid.), and liposome-mediated transfection(Hawley-Nelson et al., Focus 15:73, 1993; Ciccarone et al., Focus 15:80,1993). The production of recombinant polypeptides in cultured mammaliancells is disclosed, for example, by Levinson et al., U.S. Pat. No.4,713,339; Hagen et al., U.S. Pat. No. 4,784,950; Palmiter et al., U.S.Pat. No. 4,579,821; and Ringold, U.S. Pat. No. 4,656,134. Suitablecultured mammalian cells include the COS-1 (ATCC No. CRL 1650), COS-7(ATCC No. CRL 1651), BHK (ATCC No. CRL 1632), BHK 570 (ATCC No. CRL10314), 293 (ATCC No. CRL 1573; Graham et al., J. Gen. Virol. 36:59-72,1977), Jurkat (ATCC No. CRL-8129), BaF3 (an interleukin-3 dependentpre-lymphoid cell line derived from murine bone marrow. See, Palaciosand Steinmetz, Cell 41: 727-34, 1985; Mathey-Prevot et al., Mol. Cell.Biol. 6: 4133-5, 1986) and Chinese hamster ovary (e.g., CHO-K1; ATCC No.CCL 61) cell lines. Additional suitable cell lines are known in the artand available from public depositories such as the American Type CultureCollection, Rockville, Md. In general, strong transcription promotersare preferred, such as promoters from SV-40 or cytomegalovirus. See,e.g., U.S. Pat. No. 4,956,288. Other suitable promoters include thosefrom metallothionein genes (U.S. Pat. Nos. 4,579,821 and 4,601,978 andthe adenovirus major late promoter.

Drug selection is generally used to select for cultured mammalian cellsinto which foreign DNA has been inserted. Such cells are commonlyreferred to as “transfectants”. Cells that have been cultured in thepresence of the selective agent and are able to pass the gene ofinterest to their progeny are referred to as “stable transfectants.” Apreferred selectable marker is a gene encoding resistance to theantibiotic neomycin. Selection is carried out in the presence of aneomycin-type drug, such as G-418 or the like. Selection systems mayalso be used to increase the expression level of the gene of interest, aprocess referred to as “amplification.” Amplification is carried out byculturing transfectants in the presence of a low level of the selectiveagent and then increasing the amount of selective agent to select forcells that produce high levels of the products of the introduced genes.A preferred amplifiable selectable marker is dihydrofolate reductase,which confers resistance to methotrexate. Other drug resistance genes(e.g., hygromycin resistance, multi-drug resistance, puromycinacetyltransferase) can also be used. Alternative markers that introducean altered phenotype, such as green fluorescent protein, or cell surfaceproteins such as CD4, CD8, Class I MHC, placental alkaline phosphatasemay be used to sort transfected cells from untransfected cells by suchmeans as FACS sorting or magnetic bead separation technology.

Other higher eukaryotic cells can also be used as hosts, including plantcells, insect cells and avian cells. The use of Agrobacterium rhizogenesas a vector for expressing genes in plant cells has been reviewed bySinkar et al., J. Biosci. (Bangalore) 11:47-58, 1987. Transformation ofinsect cells and production of foreign polypeptides therein is disclosedby Guarino et al., U.S. Pat. No. 5,162,222 and WIPO publication WO94/06463. Insect cells can be infected with recombinant baculovirus,commonly derived from Autographa californica nuclear polyhedrosis virus(AcNPV). See, King and Possee, The Baculovirus Expression System: ALaboratory Guide, London, Chapman & Hall; O'Reilly et al., BaculovirusExpression Vectors: A Laboratory Manual, New York, Oxford UniversityPress., 1994; and Richardson, Ed., Baculovirus Expression Protocols.Methods in Molecular Biology, Totowa, N.J., Humana Press, 1995. A secondmethod of making recombinant BR43x2 baculovirus utilizes atransposon-based system described by Luckow (Luckow, et al., J Virol.67:4566-79, 1993). This system, which utilizes transfer vectors, is soldin the Bac-to-Bac™ kit (Life Technologies, Rockville, Md.). This systemutilizes a transfer vector, pFastBac1™ (Life Technologies) containing aTn7 transposon to move the DNA encoding the BR43x2 polypeptide into abaculovirus genome maintained in E. coli as a large plasmid called a“bacmid.” See, Hill-Perkins and Possee, J. Gen. Virol. 71:971-6, 1990;Bonning, et al., J. Gen. Virol. 75:1551-6, 1994; and, Chazenbalk, andRapoport, J. Biol. Chem. 270:1543-9, 1995. In addition, transfer vectorscan include an in-frame fusion with DNA encoding an epitope tag at theC- or N-terminus of the expressed BR43x2 polypeptide, for example, aGlu-Glu epitope tag (Grussenmeyer et al., Proc. Natl. Acad. Sci.82:7952-4, 1985). Using a technique known in the art, a transfer vectorcontaining BR43x2 is transformed into E. coli, and screened for bacmidswhich contain an interrupted lacZ gene indicative of recombinantbaculovirus. The bacmid DNA containing the recombinant baculovirusgenome is isolated, using common techniques, and used to transfectSpodoptera frugiperda cells, e.g. Sf9 cells. Recombinant virus thatexpresses BR43x2 is subsequently produced. Recombinant viral stocks aremade by methods commonly used the art.

The recombinant virus is used to infect host cells, typically a cellline derived from the fall armyworm, Spodoptera frugiperda. See, ingeneral, Glick and Pasternak, Molecular Biotechnology: Principles andApplications of Recombinant DNA, ASM Press, Washington, D.C., 1994.Another suitable cell line is the High FiveO™ cell line (Invitrogen)derived from Trichoplusia ni (U.S. Pat. No. 5,300,435). Commerciallyavailable serum-free media are used to grow and maintain the cells.Suitable media are Sf900 II™ (Life Technologies) or ESF 921™ (ExpressionSystems) for the Sf9 cells; and Ex-cellO405™ (JRH Biosciences, Lenexa,Kans.) or Express FiveO™ (Life Technologies) for the T. ni cells. Thecells are grown up from an inoculation density of approximately 2-5×10⁵cells to a density of 1-2×10⁶ cells at which time a recombinant viralstock is added at a multiplicity of infection (MOI) of 0.1 to 10, moretypically near 3. Procedures used are generally described in availablelaboratory manuals (King and Possee, ibid.; O'Reilly, et al., ibid.;Richardson, ibid.). Subsequent purification of the BR43x2 polypeptidefrom the supernatant can be achieved using methods described herein.

Fungal cells, including yeast cells, can also be used within the presentinvention. Yeast species of particular interest in this regard includeSaccharomyces cerevisiae, Pichia pastoris, and Pichia methanolica.Methods for transforming S. cerevisiae cells with exogenous DNA andproducing recombinant polypeptides there from are disclosed by, forexample, Kawasaki, U.S. Pat. No. 4,599,311; Kawasaki et al., U.S. Pat.No. 4,931,373; Brake, U.S. Pat. No. 4,870,008; Welch et al., U.S. Pat.No. 5,037,743; and Murray et al., U.S. Pat. No. 4,845,075. Transformedcells are selected by phenotype determined by the selectable marker,commonly drug resistance or the ability to grow in the absence of aparticular nutrient (e.g., leucine). A preferred vector system for usein Saccharomyces cerevisiae is the POT1 vector system disclosed byKawasaki et al. (U.S. Pat. No. 4,931,373), which allows transformedcells to be selected by growth in glucose-containing media. Suitablepromoters and terminators for use in yeast include those from glycolyticenzyme genes (see, e.g., Kawasaki, U.S. Pat. No. 4,599,311; Kingsman etal., U.S. Pat. No. 4,615,974; and Bitter, U.S. Pat. No. 4,977,092) andalcohol dehydrogenase genes. See also U.S. Pat. Nos. 4,990,446;5,063,154; 5,139,936 and 4,661,454. Transformation systems for otheryeasts, including Hansenula polymorpha, Schizosaccharomyces pombe,Kluyveromyces lactis, Kluyveromyces fragilis, Ustilago maydis, Pichiapastoris, Pichia methanolica, Pichia guillermondii and Candida maltosaare known in the art. See, for example, Gleeson et al., J. Gen.Microbiol. 132:3459-65, 1986 and Cregg, U.S. Pat. No. 4,882,279.Aspergillus cells may be utilized according to the methods of McKnightet al., U.S. Pat. No. 4,935,349. Methods for transforming Acremoniumchrysogenum are disclosed by Sumino et al., U.S. Pat. No. 5,162,228.Methods for transforming Neurospora are disclosed by Lambowitz, U.S.Pat. No. 4,486,533.

For example, the use of Pichia methanolica as host for the production ofrecombinant proteins is disclosed by Raymond, U.S. Pat. No. 5,716,808,Raymond, U.S. Pat. No. 5,736,383, Raymond et al., Yeast 14:11-23, 1998,and in international publication Nos. WO 97/17450, WO 97/17451, WO98/02536, and WO 98/02565. DNA molecules for use in transforming P.methanolica will commonly be prepared as double-stranded, circularplasmids, which are preferably linearized prior to transformation. Forpolypeptide production in P. methanolica, it is preferred that thepromoter and terminator in the plasmid be that of a P. methanolica gene,such as a P. methanolica alcohol utilization gene (AUG1 or AUG2). Otheruseful promoters include those of the dihydroxyacetone synthase (DHAS),formate dehydrogenase (FMD), and catalase (CAT) genes. To facilitateintegration of the DNA into the host chromosome, it is preferred to havethe entire expression segment of the plasmid flanked at both ends byhost DNA sequences. A preferred selectable marker for use in Pichiamethanolica is a P. methanolica ADE2 gene, which encodesphosphoribosyl-5-aminoimidazole carboxylase (AIRC; EC 4.1.1.21), whichallows ade2 host cells to grow in the absence of adenine. Forlarge-scale, industrial processes where it is desirable to minimize theuse of methanol, it is preferred to use host cells in which bothmethanol utilization genes (AUG1 and AUG2) are deleted. For productionof secreted proteins, host cells deficient in vacuolar protease genes(PEP4 and PRB1) are preferred. Electroporation is used to facilitate theintroduction of a plasmid containing DNA encoding a polypeptide ofinterest into P. methanolica cells. It is preferred to transform P.methanolica cells by electroporation using an exponentially decaying,pulsed electric field having a field strength of from 2.5 to 4.5 kV/cm,preferably about 3.75 kV/cm, and a time constant (t) of from 1 to 40milliseconds, most preferably about 20 milliseconds.

Prokaryotic host cells, including strains of the bacteria Escherichiacoli, Bacillus and other genera are also useful host cells within thepresent invention. Techniques for transforming these hosts andexpressing foreign DNA sequences cloned therein are well known in theart (see, e.g., Sambrook et al., ibid.). When expressing a BR43x2polypeptide in bacteria such as E. coli, the polypeptide may be retainedin the cytoplasm, typically as insoluble granules, or may be directed tothe periplasmic space by a bacterial secretion sequence. In the formercase, the cells are lysed, and the granules are recovered and denaturedusing, for example, guanidine isothiocyanate or urea. The denaturedpolypeptide can then be refolded and dimerized by diluting thedenaturant, such as by dialysis against a solution of urea and acombination of reduced and oxidized glutathione, followed by dialysisagainst a buffered saline solution. In the latter case, the polypeptidecan be recovered from the periplasmic space in a soluble and functionalform by disrupting the cells (by, for example, sonication or osmoticshock) to release the contents of the periplasmic space and recoveringthe protein, thereby obviating the need for denaturation and refolding.

Transformed or transfected host cells are cultured according toconventional procedures in a culture medium containing nutrients andother components required for the growth of the chosen host cells. Avariety of suitable media, including defined media and complex media,are known in the art and generally include a carbon source, a nitrogensource, essential amino acids, vitamins and minerals. Media may alsocontain such components as growth factors or serum, as required. Thegrowth medium will generally select for cells containing the exogenouslyadded DNA by, for example, drug selection or deficiency in an essentialnutrient which is complemented by the selectable marker carried on theexpression vector or co-transfected into the host cell. P. methanolicacells are cultured in a medium comprising adequate sources of carbon,nitrogen and trace nutrients at a temperature of about 25° C. to 35° C.Liquid cultures are provided with sufficient aeration by conventionalmeans, such as shaking of small flasks or sparging of fermentors. Apreferred culture medium for P. methanolica is YEPD (2% D-glucose, 2%Bacto™ Peptone (Difco Laboratories, Detroit, Mich.), 1% Bacto™ yeastextract (Difco Laboratories), 0.004% adenine and 0.006% L-leucine).

Expressed recombinant BR43x2 polypeptides (or chimeric or fusion BR43x2polypeptides) can be purified using fractionation and/or conventionalpurification methods and media. It is preferred to provide the proteinsor polypeptides of the present invention in a highly purified form, i.e.greater than 95% pure, more preferably greater than 99% pure. Ammoniumsulfate precipitation and acid or chaotrope extraction may be used forfractionation of samples. Exemplary purification steps may includehydroxyapatite, size exclusion, FPLC and reverse-phase high performanceliquid chromatography. Suitable anion exchange media include derivatizeddextrans, agarose, cellulose, polyacrylamide, specialty silicas, and thelike. PEI, DEAE, QAE and Q derivatives are preferred, with DEAEFast-Flow Sepharose (Pharmacia, Piscataway, N.J.) being particularlypreferred. Exemplary chromatographic media include those mediaderivatized with phenyl, butyl, or octyl groups, such asPhenyl-Sepharose FF (Pharmacia), Toyopearl butyl 650 (Toso Haas,Montgomeryville, Pa.), Octyl-Sepharose (Pharmacia) and the like; orpolyacrylic resins, such as Amberchrom CG 71 (Toso Haas) and the like.Suitable solid supports include glass beads, silica-based resins,cellulosic resins, agarose beads, cross-linked agarose beads,polystyrene beads, cross-linked polyacrylamide resins and the like thatare insoluble under the conditions in which they are to be used. Thesesupports may be modified with reactive groups that allow attachment ofproteins by amino groups, carboxyl groups, sulfhydryl groups, hydroxylgroups and/or carbohydrate moieties. Examples of coupling chemistriesinclude cyanogen bromide activation, N-hydroxysuccinimide activation,epoxide activation, sulfhydryl activation, hydrazide activation, andcarboxyl and amino derivatives for carbodiimide coupling chemistries.These and other solid media are well known and widely used in the art,and are available from commercial suppliers. Methods for bindingreceptor polypeptides to support media are well known in the art.Selection of a particular method is a matter of routine design and isdetermined in part by the properties of the chosen support. See, forexample, Affinity Chromatography Principles & Methods, Pharmacia LKBBiotechnology, Uppsala, Sweden, 1988.

The polypeptides of the present invention can be isolated byexploitation of their physical properties. For example, immobilizedmetal ion adsorption (IMAC) chromatography can be used to purifyhistidine-rich proteins including those comprising polyhistidine tags.Briefly, a gel is first charged with divalent metal ions to form achelate (Sulkowski, Trends in Biochem. 3:1-7, 1985). Histidine-richproteins will be adsorbed to this matrix with differing affinities,depending upon the metal ion used, and will be eluted by competitiveelution, lowering the pH, or use of strong chelating agents. Othermethods of purification include purification of glycosylated proteins bylectin affinity chromatography and ion exchange chromatography (Methodsin Enzymol., Vol. 182, “Guide to Protein Purification”, M. Deutscher,(ed.), Acad. Press, San Diego, 1990, pp. 529-39). Within additionalembodiments of the invention, a fusion of the polypeptide of interestand an affinity tag (e.g., maltose-binding protein, FLAG-tag (Asp TyrLys Asp Asp Asp Asp Lys (SEQ ID NO:13)), Glu-Glu tag (Glu Glu Tyr MetPro Met Glu (SEQ ID NO:14)), an immunoglobulin domain) may beconstructed to facilitate purification.

Protein refolding (and optionally reoxidation) procedures may beadvantageously used. It is preferred to purify the protein to >80%purity, more preferably to >90% purity, even more preferably >95%, andparticularly preferred is a pharmaceutically pure state, that is greaterthan 99.9% pure with respect to contaminating macromolecules,particularly other proteins and nucleic acids, and free of infectiousand pyrogenic agents. Preferably, a purified protein is substantiallyfree of other proteins, particularly other proteins of animal origin.

BR43x2 polypeptides or fragments thereof may also be prepared throughchemical synthesis. BR43x2 polypeptides may be monomers or multimers;glycosylated or non-glycosylated; pegylated or non-pegylated; and may ormay not include an initial methionine amino acid residue. ExemplaryBR43x2 polypeptides include polypeptides of from 32-40 residues inlength having an amino acid sequence conforming to the motif:XXCX[QEK][QEKNRDHS][QE]X{0-2}[YFW][YFW]DXLLX{2}C[IMLV]XCX{3}CX{6-8}CX{2}[YF)CXX(SEQ ID NO:10), and subject to the limitations described herein.

BR43x2 polypeptides can be synthesized by exclusive solid phasesynthesis, partial solid phase methods, fragment condensation orclassical solution synthesis. The polypeptides are preferably preparedby solid phase peptide synthesis, for example as described byMerrifield, J. Am. Chem. Soc. 85:2149, 1963. The synthesis is carriedout with amino acids that are protected at the alpha-amino terminus.Trifunctional amino acids with labile side-chains are also protectedwith suitable groups to prevent undesired chemical reactions fromoccurring during the assembly of the polypeptides. The alpha-aminoprotecting group is selectively removed to allow subsequent reaction totake place at the amino-terminus. The conditions for the removal of thealpha-amino protecting group do not remove the side-chain protectinggroups.

The alpha-amino protecting groups are those known to be useful in theart of stepwise polypeptide synthesis. Included are acyl type protectinggroups (e.g., formyl, trifluoroacetyl, acetyl), aryl type protectinggroups (e.g., biotinyl), aromatic urethane type protecting groups [e.g.,benzyloxycarbonyl (Cbz), substituted benzyloxycarbonyl and9-fluorenylmethyloxycarbonyl (Fmoc)], aliphatic urethane protectinggroups [e.g., t-butyloxycarbonyl (tBoc), isopropyl-oxycarbonyl,cyclohexloxycarbonyl] and alkyl type protecting groups (e.g., benzyl,triphenylmethyl). The preferred protecting groups are tBoc and Fmoc.

The side-chain protecting groups selected must remain intact duringcoupling and not be removed during the deprotection of theamino-terminus protecting group or during coupling conditions. Theside-chain protecting groups must also be removable upon the completionof synthesis using reaction conditions that will not alter the finishedpolypeptide. In tBoc chemistry, the side-chain protecting groups fortrifunctional amino acids are mostly benzyl based. In Fmoc chemistry,they are mostly tert-butyl or trityl based.

In tBoc chemistry, the preferred side-chain protecting groups are tosylfor arginine, cyclohexyl for aspartic acid, 4-methylbenzyl (andacetamidomethyl) for cysteine, benzyl for glutamic acid, serine andthreonine, benzyloxymethyl (and dinitrophenyl) for histidine,2-Cl-benzyloxycarbonyl for lysine, formyl for tryptophan and2-bromobenzyl for tyrosine. In Fmoc chemistry, the preferred side-chainprotecting groups are 2,2,5,7,8-pentamethylchroman-6-sulfonyl (Pmc) or2,2,4,6,7-penta-methyldihydrobenzofuran-5-sulfonyl (Pbf) for arginine,trityl for asparagine, cysteine, glutamine and histidine, tert-butyl foraspartic acid, glutamic acid, serine, threonine and tyrosine, tBoc forlysine and tryptophan.

For the synthesis of phosphopeptides, either direct or post-assemblyincorporation of the phosphate group is used. In the directincorporation strategy, the phosphate group on serine, threonine ortyrosine may be protected by methyl, benzyl, or tert-butyl in Fmocchemistry or by methyl, benzyl or phenyl in tBoc chemistry. Directincorporation of phosphotyrosine without phosphate protection can alsobe used in Fmoc chemistry. In the post-assembly incorporation strategy,the unprotected hydroxyl groups of serine, threonine or tyrosine arederivatized on solid phase with di-tert-butyl-, dibenzyl- ordimethyl-N,N′-diisopropyl-phosphoramidite and then oxidized bytert-butylhydroperoxide.

Solid phase synthesis is usually carried out from the carboxyl-terminusby coupling the alpha-amino protected (side-chain protected) amino acidto a suitable solid support. An ester linkage is formed when theattachment is made to a chloromethyl, chlorotrityl or hydroxymethylresin, and the resulting polypeptide will have a free carboxyl group atthe C-terminus. Alternatively, when an amide resin such asbenzhydrylamine or p-methylbenzhydrylamine resin (for tBoc chemistry)and Rink amide or PAL resin (for Fmoc chemistry) are used, an amide bondis formed and the resulting polypeptide will have a carboxamide group atthe C-terminus. These resins, whether polystyrene- or polyamide-based orpolyethyleneglycol-grafted, with or without a handle or linker, with orwithout the first amino acid attached, are commercially available, andtheir preparations have been described by Stewart et al., “Solid PhasePeptide Synthesis” (2nd Edition), (Pierce Chemical Co., Rockford, Ill.,1984) and Bayer and Rapp, Chem. Pept. Prot. 3:3, 1986; and Atherton etal., Solid Phase Peptide Synthesis: A Practical Approach, IRL Press,Oxford, 1989.

The C-terminal amino acid, protected at the side chain if necessary, andat the alpha-amino group, is attached to a hydroxylmethyl resin usingvarious activating agents including dicyclohexylcarbodiimide (DCC),N,N′-diisopropylcarbodiimide (DIPCDI) and carbonyldiimidazole (CDI). Itcan be attached to chloromethyl or chlorotrityl resin directly in itscesium tetramethylammonium salt form or in the presence of triethylamine(TEA) or diisopropylethylamine (DIEA). First amino acid attachment to anamide resin is the same as amide bond formation during couplingreactions.

Following the attachment to the resin support, the alpha-aminoprotecting group is removed using various reagents depending on theprotecting chemistry (e.g., tBoc, Fmoc). The extent of Fmoc removal canbe monitored at 300-320 nm or by a conductivity cell. After removal ofthe alpha-amino protecting group, the remaining protected amino acidsare coupled stepwise in the required order to obtain the desiredsequence.

Various activating agents can be used for the coupling reactionsincluding DCC, DIPCDI, 2-chloro-1,3-dimethylimidium hexafluorophosphate(CIP), benzotriazol-1-yl-oxy-tris-(dimethyl-amino)-phosphoniumhexafluoro-phosphate (BOP) and its pyrrolidine analog (PyBOP),bromo-tris-pyrrolidino-phosphonium hexafluorophosphate (PyBrOP),O-(benzotriazol-1-yl)-1,1,3,3-tetramethyluronium hexafluorophosphate(HBTU) and its tetra-fluoroborate analog (TBTU) or its pyrrolidineanalog (HBPyU), O-(7-azabenzotriazol-1-yl)-1,1,3,3-tetramethyl-uroniumhexafluoro-phosphate (HATU) and its tetrafluoroborate analog (TATU) orits pyrrolidine analog (HAPyU). The most common catalytic additives usedin coupling reactions include 4-dimethylaminopyridine (DMAP),3-hydroxy-3,4-dihydro-4-oxo-1,2,3-benzotriazine (HODhbt),N-hydroxybenzotriazole (HOBt) and 1-hydroxy-7-azabenzotriazole (HOAt).Each protected amino acid is used in excess (>2.0 equivalents), and thecouplings are usually carried out in N-methylpyrrolidone (NMP) or inDMF, CH₂Cl₂ or mixtures thereof. The extent of completion of thecoupling reaction can be monitored at each stage, e.g., by the ninhydrinreaction as described by Kaiser et al., Anal. Biochem. 34:595, 1970.

After the entire assembly of the desired peptide, the peptide-resin iscleaved with a reagent with proper scavengers. The Fmoc peptides areusually cleaved and deprotected by TFA with scavengers (e.g., H₂O,ethanedithiol, phenol and thioanisole). The tBoc peptides are usuallycleaved and deprotected with liquid HF for 1-2 hours at −5 to 0° C.,which cleaves the polypeptide from the resin and removes most of theside-chain protecting groups. Scavengers such as anisole,dimethylsulfide and p-thiocresol are usually used with the liquid HF toprevent cations formed during the cleavage from alkylating and acylatingthe amino acid residues present in the polypeptide. The formyl group oftryptophan and the dinitrophenyl group of histidine need to be removed,respectively by piperidine and thiophenyl in DMF prior to the HFcleavage. The acetamidomethyl group of cysteine can be removed bymercury(II)acetate and alternatively by iodine, thallium(III)trifluoroacetate or silver tetrafluoroborate which simultaneouslyoxidize cysteine to cystine. Other strong acids used for tBoc peptidecleavage and deprotection include trifluoromethanesulfonic acid (TFMSA)and trimethylsilyl-trifluoroacetate (TMSOTf).

The present invention further provides a variety of other polypeptidefusions and related multimeric proteins comprising one or morepolypeptide fusions. A soluble BR43x2, TACI or BCMA polypeptide can beexpressed as a fusion with an immunoglobulin heavy chain constantregion, typically an F_(c) fragment, which contains two constant regiondomains and lacks the variable region. Methods for preparing suchfusions are disclosed in U.S. Pat. Nos. 5,155,027 and 5,567,584. Suchfusions are typically secreted as multimeric molecules wherein the Fcportions are disulfide bonded to each other and two non-Ig polypeptidesare arrayed in close proximity to each other. Immunoglobulin-BR43x2(TACI or BCMA) polypeptide fusions can be expressed in geneticallyengineered cells to produce a variety of multimeric BR43x2 analogs.Auxiliary domains can be fused to BR43x2 (TACI or BCMA) polypeptides totarget them to specific cells, tissues, or macromolecules. Fusions mayalso be made using toxins as discussed herein. In this way, polypeptidesand proteins can be targeted for therapeutic or diagnostic purposes. ABR43x2 polypeptide can be fused to two or more moieties, such as anaffinity tag for purification and a targeting domain. Polypeptidefusions can also comprise one or more cleavage sites, particularlybetween domains. See, Tuan et al., Connect. Tiss. Res. 34:1-9, 1996.Fusions of this type can also be used, for example, to affinity purifycognate ligand from a solution, as an in vitro assay tool, to blocksignals in vitro by specifically titrating out ligand, to bind ligand onthe cell surface or as a BR43x2 antagonists in vivo by administeringthem to block ligand stimulation. For use in assays, the fusion proteinsmay be bound to a support via the F_(c) region and used in an ELISAformat.

The invention also provides soluble BR43x2 receptors and polypeptidefragments used to form fusion proteins with affinity tags or labels.Soluble BR43x2-affinity tag fusion proteins are used, for example, toidentify the BR43x2 ligands, as well as agonists and antagonists of thenatural ligand. Using labeled, soluble BR43x2, cells expressing theligand, agonists or antagonists are identified by fluorescenceimmunocytometry or immunohistochemistry. The soluble fusion proteins areuseful in studying the distribution of the ligand on tissues or specificcell lineages, and to provide insight into receptor/ligand biology.

To purify ligand, agonists or antagonists, a BR43x2-Ig fusion protein isadded to a sample containing the ligand, agonist or antagonist underconditions that facilitate receptor-ligand binding (typicallynear-physiological temperature, pH, and ionic strength). Thereceptor-ligand complex is then separated by the mixture using proteinA, which is immobilized on a solid support (e.g., insoluble resinbeads). The ligand, agonist, antagonist is then eluted usingconventional chemical techniques, such as with a salt or pH gradient. Inthe alternative, the fusion protein itself can be bound to a solidsupport, with binding and elution carried out as above. Methods forimmobilizing receptor polypeptide to a solid support, such as beads ofagarose, cross-linked agarose, glass, cellulosic resins, silica-basedresins, polystyrene, cross-linked polyacrylamide, or like materials thatare stable under the conditions of use are known in the art. Methods forlinking polypeptides to solid supports are known in the art, and includeamine chemistry, cyanogen bromide activation, N-hydroxysuccinimideactivation, epoxide activation, sulfhydryl activation, and hydrazideactivation. The resulting media will generally be configured in the formof a column, and fluids containing ligand are passed through the columnone or more times to allow ligand to bind to the receptor polypeptide.The ligand is then eluted using changes in salt concentration,chaotropic agents (MnCl₂), or pH to disrupt ligand-receptor binding.

To direct the export of the soluble receptor from the host cell, thesoluble receptor DNA is linked to a second DNA segment encoding asecretory peptide, such as a t-PA secretory peptide. To facilitatepurification of the secreted receptor domain, an N- or C-terminalextension, such as an affinity tag or another polypeptide or protein forwhich an antibody or other specific binding agent is available, can befused to the receptor polypeptide.

Cells expressing functional soluble and membrane bound receptors of thepresent invention are used within screening assays. A variety ofsuitable assays are known in the art. These assays are based on thedetection of a biological response in a target cell. A change inmetabolism compared to a control value indicates a test compound thatmodulates BR43x2 mediated metabolism. One such assay is a cellproliferation assay. Cells are cultured in the presence or absence of atest compound, and cell proliferation is detected by, for example,measuring incorporation of tritiated thymidine or by colorimetric assaybased on the metabolic breakdown of3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT)(Mosman, J. Immunol. Meth. 65: 55-63, 1983). An alternative assay formatuses cells that are further engineered to express a reporter gene. Thereporter gene is linked to a promoter element that is responsive to thereceptor-linked pathway, and the assay detects activation oftranscription of the reporter gene. Numerous reporter genes that areeasily assayed for in cell extracts are known in the art, for example,the E. coli lacZ, chloroamphenicol acetyl transferase (CAT) and serumresponse element (SRE) (see, e.g., Shaw et al., Cell 56:563-72, 1989). Apreferred such reporter gene is a luciferase gene (de Wet et al., Mol.Cell. Biol. 7:725, 1987). Expression of the luciferase gene is detectedby luminescence using methods known in the art (e.g., Baumgartner etal., J. Biol. Chem. 269:29094-101, 1994; Schenborn and Goiffin, PromegaNotes 41:11, 1993). Luciferase activity assay kits are commerciallyavailable from, for example, Promega Corp., Madison, Wis. Target celllines of this type can be used to screen libraries of chemicals,cell-conditioned culture media, fungal broths, soil samples, watersamples, and the like. For example, a bank of cell-conditioned mediasamples can be assayed on a target cell to identify cells that produceligand. Positive cells are then used to produce a cDNA library in amammalian expression vector, which is divided into pools, transfectedinto host cells, and expressed. Media samples from the transfected cellsare then assayed, with subsequent division of pools, re-transfection,subculturing, and re-assay of positive cells to isolate a cloned cDNAencoding the ligand.

An assay system that uses a ligand-binding receptor (or an antibody, onemember of a complement/anti-complement pair) or a binding fragmentthereof, and a commercially available biosensor instrument (BIAcore™,Pharmacia Biosensor, Piscataway, N.J.) may also may be advantageouslyemployed. Such receptor, antibody, member of acomplement/anti-complement pair or fragment is immobilized onto thesurface of a receptor chip. Use of this instrument is disclosed byKarlsson, J. Immunol. Meth. 145:229-40, 1991 and Cunningham and Wells,J. Mol. Biol. 234:554-63, 1993. For example, a BR43x2 polypeptide,fragment, antibody or member of a complement/anti-complement pair iscovalently attached, using amine or sulfhydryl chemistry, to dextranfibers that are attached to gold film within the flow cell. A testsample is passed through the cell. If a ligand, epitope, or oppositemember of the complement/anti-complement pair is present in the sample,it will bind to the immobilized receptor, antibody or member,respectively, causing a change in the refractive index of the medium,which is detected as a change in surface plasmon resonance of the goldfilm. This system allows the determination of on- and off-rates, fromwhich binding affinity can be calculated, and assessment ofstoichiometry of binding. Ligand-binding receptor polypeptides can alsobe used within other assay systems known in the art. Such systemsinclude Scatchard analysis for determination of binding affinity (see,Scatchard, Ann. NY Acad. Sci. 51: 660-72, 1949) and calorimetric assays(Cunningham et al., Science 253:545-48, 1991; Cunningham et al., Science245:821-25, 1991).

Scatchard plot analysis for soluble I¹²⁵-ztnf4 binding to TACI and BCMAis shown in FIG. 2 and compared with the binding constants of othermembers of the TNFR family in Table 5.

TABLE 5 Ligand Kd M Cell source Reference TNFa high 7.14E−11 HL-60 aTNFa low 3.26E−10 HEP-2 a TNFa high 2.00E−10 HL-60 b CD27L 3.70E−10 MP-1c CD27L 8.30E−09 MP-1 c CD40L 5.00E−10 EL40.5 d CD40L 1.00E−09 EBNA d(125I-CD40) 4-1BBL 1.16E−09 Biacore e anti 41BBmab 4.14E−10 Biacore eztnf4 sol. 1.11E−09 TACI-BHK ztnf4 sol. 1.25E−09 BCMA-BHKa Hohmann et al., J. Biol. Chem. 264:14927-34, 1989b Manna and Aggarwal, J. Biol. Chem. 273:33333-41, 1998c Goodwin et al., Cell 73:447-56, 1993d Armitage et al., Nature 357:80-82, 1992e Shuford et al., J. Exp. Med. 186:47-55, 1997

As a receptor, the activation of BR43x2 polypeptide can be measured by asilicon-based biosensor microphysiometer which measures theextracellular acidification rate or proton excretion associated withreceptor binding and subsequent physiologic cellular responses. Anexemplary device is the Cytosensor™ Microphysiometer manufactured byMolecular Devices, Sunnyvale, Calif. A variety of cellular responses,such as cell proliferation, ion transport, energy production,inflammatory response, regulatory and receptor activation, and the like,can be measured by this method. See, for example, McConnell et al.,Science 257:1906-12, 1992; Pitchford et al., Meth. Enzymol. 228:84-108,1997; Arimilli et al., J. Immunol. Meth. 212:49-59, 1998; Van Liefde etal., Eur. J. Pharmacol. 346:87-95, 1998. The microphysiometer can beused for assaying adherent or non-adherent eukaryotic or prokaryoticcells. By measuring extracellular acidification changes in cell mediaover time, the microphysiometer directly measures cellular responses tovarious stimuli, including agonists, ligands, or antagonists of theBR43x2 polypeptide. Preferably, the microphysiometer is used to measureresponses of a BR43x2-expressing eukaryotic cell, compared to a controleukaryotic cell that does not express BR43x2 polypeptide.BR43x2-expressing eukaryotic cells comprise cells into which BR43x2 hasbeen transfected, as described herein, creating a cell that isresponsive to BR43x2-modulating stimuli; or cells naturally expressingBR43x2, such as BR43x2-expressing cells derived from spleen tissue.Differences, measured by a change in extracellular acidification, forexample, an increase or diminution in the response of cells expressingBR43x2, relative to a control, are a direct measurement ofBR43x2-modulated cellular responses. Moreover, such BR43x2-modulatedresponses can be assayed under a variety of stimuli. Also, using themicrophysiometer, there is provided a method of identifying agonists andantagonists of BR43x2 polypeptide, comprising providing cells expressinga BR43x2 polypeptide, culturing a first portion of the cells in theabsence of a test compound, culturing a second portion of the cells inthe presence of a test compound, and detecting a change, for example, anincrease or diminution, in a cellular response of the second portion ofthe cells as compared to the first portion of the cells. The change incellular response is shown as a measurable change extracellularacidification rate. Antagonists and agonists for BR43x2 polypeptide canbe rapidly identified using this method.

The soluble BR43x2 is useful in studying the distribution of ligands ontissues or specific cell lineages, and to provide insight intoreceptor/ligand biology. Application may also be made of the specificityof TNF receptors for their ligands as a mechanism by which to destroyligand-bearing target cells. For example, toxic compounds may be coupledto BR43x2 soluble receptor or BR43x2 fusion. Examples of toxic compoundswould include radiopharmaceuticals that inactivate target cells;chemotherapeutic agents such as doxorubicin, daunorubicin, methotrexate,and cytoxan; toxins, such as ricin, diphtheria, Pseudomonas exotoxin Aand abrin; and antibodies to cytotoxic T-cell surface molecules.

Ztnf4 (5 ng/ml) was found to bind to BR43x2 (SEQ ID NO:2), TACI (SEQ IDNO:6), BCMA (SEQ ID NO:8) and BR43x1 (SEQ ID NO:9), by FACS analysis(Flow Cytometry and Sorting, Melamed et al. eds. Wiley-Liss, 1990 andImmunofluorescence and Cell Sorting, Current Protocols in Immunology,Volume 1, Coligan et al. eds. John Wiley & Son, 1997). FITC-tagged,soluble ztnf4 was also shown to bind specifically to, among otherthings, B lymphocytes in PBMNCs, tonsil cells, to B cell lymphoma celllines (Raji, Burkitt's human lymphoma, ATCC CCL86), Ramos (Burkitt'slymphoma cell line, ATCC CRL-1596), Daudi (Burkitt's human lymphoma,ATCC CCL213) and RPMI 1788 (a B lymphocyte cell line, ATCC CCL-156)using FACS analysis. No binding was seen with HL-60, (ATCC apromyelocytic cell line, ATCC CCL-240). Specificity for binding to Bcells from PBMNC and tonsil cells was confirmed by co-staining withantibodies to B cell specific molecules including CD19, IgD, IgM, andCD20. Similarity of ztnf4 to CD40L suggested a broader tissuedistribution than was seen. Affinity of ztnf4 was tested on monocytes,dendritic cells, and purified T cells using cytokine proliferation and Tcell proliferation assays, for example, and could not detect binding ofztnf4 or any other biological effect on any other type of cell tested.Therefore, the specificity for B cells by the ligand and receptorsuggests that they are useful for the study and treatment ofautoimmunity, B cell cancers, immunomodulation, IBD and anyantibody-mediated pathologies, e.g. ITCP, myasthenia gravis and thelike, renal diseases, indirect T cell immune response, graft rejection,graft versus host disease.

Ztnf4 has been shown to activate B cells resulting in B cellproliferation, antibody production and up-regulation of activationmarkers in vitro (see examples below). These affects may requireco-stimulation via IL-4 or other cytokines or stimulation through the Bcell antigen receptor or other cell surface receptors which activate Bcells, i.e., CD40. Other tumor necrosis factor ligands, such as gp39 andTNFβ, also stimulate B cell proliferation. Thus the polypeptides of thecurrent invention can be targeted to specifically regulate B cellresponses, inhibiting activated B cells, during the immune responsewithout affecting other cell populations which is advantageous in thetreatment of disease. Additionally, the polypeptides of the presentinvention could be used to modulate B cell development, development ofother cells, antibody production and cytokine production. BR43x2polypeptides can also find use in inducing apoptosis and/or anergywithin cells. Polypeptides of the present invention could also modulateT and B cell communication by neutralizing the proliferative effects ofztnf4. Bioassays and ELISAs are available to measure cellular responseto ztnf4 in the presence of soluble BR43x2, TACI and/or BCMA. Otherassays include those which measure changes in cytokine production as ameasure of cellular response (see for example, Current Protocols inImmunology ed. John E. Coligan et al., NIH, 1996). Assays to measureother cellular responses, including antibody isotype, monocyteactivation, NK cell formation, antigen presenting cell function,apoptosis.

BR43x2 polypeptides of the present invention would be useful toneutralize the effects of ztnf4 for treating pre-B or B-cell leukemias,such as plasma cell leukemia, chronic or acute lymphocytic leukemia,myelomas such as multiple myeloma, plasma cell myeloma, endothelialmyeloma and giant cell myeloma; and lymphomas such as non-Hodgkinslymphoma, for which an increase in ztnf4 polypeptides is associated.Soluble BR43x2 would be a useful component in a therapy regime forinhibiting tumor progression and survival.

Northern blot analysis showed ztnf4 is expressed in CD8⁺ cells,monocytes, dendritic cells, activated monocytes. This suggests that insome autoimmune disorders, cytotoxic T-cells might stimulate B-cellproduction through excess production of ztnf4. Immunosuppressantproteins that selectively block the action of B-lymphocytes would be ofuse in treating disease. Autoantibody production is common to severalautoimmune diseases and contributes to tissue destruction andexacerbation of disease. Autoantibodies can also lead to the occurrenceof immune complex deposition complications and lead to many symptoms ofsystemic lupus erythomatosis, including kidney failure, neuralgicsymptoms and death. Modulating antibody production independent ofcellular response would also be beneficial in many disease states. Bcells have also been shown to play a role in the secretion ofarthritogenic immunoglobulins in rheumatoid arthritis, (Korganow et al.,Immunity 10:451-61, 1999). As such, inhibition of ztnf4 antibodyproduction would be beneficial in treatment of autoimmune diseases suchas myasthenia gravis and rheumatoid arthritis. Immunosuppressanttherapeutics such as soluble BR43x2 that selectively block or neutralizethe action of B-lymphocytes would be useful for such purposes. To verifythese capabilities in BR43x2 soluble receptor polypeptides of thepresent invention, such BR43x2 polypeptides are evaluated using assaysknown in the art and described herein.

The invention provides methods employing BR43x2, TACI or BCMApolypeptides, fusions, antibodies, agonists or antagonists forselectively blocking or neutralizing the actions of B-cells inassociation with end stage renal diseases, which may or may not beassociated with autoimmune diseases. Such methods would also be usefulfor treating immunologic renal diseases. Such methods would be would beuseful for treating glomerulonephritis associated with diseases such asmembranous nephropathy, IgA nephropathy or Berger's Disease, IgMnephropathy, Goodpasture's Disease, post-infectious glomerulonephritis,mesangioproliferative disease, chronic lymphoid leukemia, minimal-changenephrotic syndrome. Such methods would also serve as therapeuticapplications for treating secondary glomerulonephritis or vasculitisassociated with such diseases as lupus, polyarteritis, Henoch-Schonlein,Scleroderma, HIV-related diseases, amyloidosis or hemolytic uremicsyndrome. The methods of the present invention would also be useful aspart of a therapeutic application for treating interstitial nephritis orpyelonephritis associated with chronic pyelonephritis, analgesic abuse,nephrocalcinosis, nephropathy caused by other agents, nephrolithiasis,or chronic or acute interstitial nephritis.

The methods of the present invention also include use of BR43x2, TACI orBCMA polypeptides, fusions, antibodies, agonists or antagonists in thetreatment of hypertensive or large vessel diseases, including renalartery stenosis or occlusion and cholesterol emboli or renal emboli.

The present invention also provides methods for diagnosis and treatmentof renal or urological neoplasms, multiple mylelomas, lymphomas, lightchain neuropathy or amyloidosis.

The invention also provides methods for blocking or inhibiting activatedB cells using BR43x2, TACI, or BCMA polypeptides, fusions, antibodies,agonists or antagonists for the treatment of asthma and other chronicairway diseases such as bronchitis and emphysema.

Also provided are methods for inhibiting or neutralizing an effector Tcell response using BR43x2, TACI, or BCMA polypeptides, fusions,antibodies, agonists or antagonists for use in immunosuppression, inparticular for such therapeutic use as for graft-versus-host disease andgraft rejection. Additional use would be found in regulation of theimmune response, in particular the activation and regulation oflymphocytes. BR43x2, TACI, or BCMA polypeptides, fusions, antibodies,agonists or antagonists would be useful in therapies for treatingimmunodeficiencies. BR43x2, TACI, or BCMA polypeptides, fusions,antibodies, agonists or antagonists would be useful in therapeuticprotocols for treatment of such autoimmune diseases as insulin dependentdiabetes mellitus (IDDM) and Crohn's Disease. Methods of the presentinvention would have additional therapeutic value for treating chronicinflammatory diseases, in particular to lessen joint pain, swelling,anemia and other associated symptoms as well as treating septic shock.

The effect of soluble BR43x2, TACI, or BCMA polypeptides and fusionproteins on immune response can be measured by administering thepolypeptides of the present invention to animals immunized with antigenfollowed by injection of ztnf4 and measuring antibody isotype productionand B and T cell responses including delayed type hypersensitivity andin vitro proliferation and cytokine production according the methodsknown in the art.

The present invention therefore provides a method of inhibiting ztnf4activity in a mammal comprising administering to said mammal an amountof a compound selected from the group consisting of: a) a polypeptide ofSEQ ID NO:4; b) a polypeptide of SEQ ID NO:8; c) a fusion protein; d) apolypeptide of SEQ ID NO:6 from amino acid residue 1 to residue 166; e)a polypeptide of SEQ ID NO:8 from amino acid residue 1 to residue 150;f) an antibody or antibody fragment which specifically binds to apolypeptide of SEQ ID NO:4; and g) an antibody or antibody fragmentwhich specifically binds to a polypeptide of SEQ ID NO:10. Examples offusion proteins include fusions of soluble BR43x2 (SEQ ID NO:4), TACI(from amino acid residue 1 to residue 166 of SEQ ID NO:6) or BCMA (fromamino acid residue 1 to residue 150 of SEQ ID NO:8) with anotherpolypeptide, preferably an immunoglobulin heavy chain constant regionF_(c) fragment. The invention similarly provides a method for inhibitingBR43x2, TACI or BCMA receptor-ligand engagement.

Such methods would be particularly useful where ztnf4 activity isassociated with activated B lymphocytes and for treating pre-B cell orB-cell cancers. Such methods would also be useful where ztnf4 activityis associated with antibody production. In particular, antibodyproduction associated with autoimmune diseases such as systemic lupuserythomatosis, myasthenia gravis or rheumatoid arthritis.

The present invention also provides BR43x2 agonists and antagonists.Compounds identified as BR43x2 agonists are useful for modifying theproliferation and development of target cells in vitro and in vivo. Forexample, agonist compounds are useful alone or in combination with othercytokines and hormones as components of defined cell culture media.Agonists are thus useful in specifically mediating the growth and/ordevelopment of BR43x2-bearing B lymphocytes cells in culture. Agonistsand antagonists may also prove useful in the study of effector functionsof B lymphocytes, in particular B lymphocyte activation anddifferentiation. Antagonists are useful as research reagents forcharacterizing ligand-receptor interaction.

Compounds identified as BR43x2 antagonists are also useful to boost thehumoral immune response. B cell responses are important in fightinginfectious diseases including bacterial, viral, protozoan and parasiticinfections. Antibodies against infectious microorganisms can immobilizethe pathogen by binding to antigen followed by complement mediated lysisor cell mediated attack. A BR43x2 antagonist would serve to boost thehumoral response and would be a useful therapeutic for individuals atrisk for an infectious disease or as a supplement to vaccination.

The invention also provides antagonists, which either bind to BR43x2polypeptides or, alternatively, to a ligand to which BR43x2 polypeptidesbind, thereby inhibiting or eliminating the function of BR43x2. SuchBR43x2 antagonists would include antibodies; oligonucleotides which bindeither to the BR43x2 polypeptide or to its ligand; natural or syntheticanalogs of BR43x2 ligands which retain the ability to bind the receptorbut do not result in either ligand or receptor signaling. Such analogscould be peptides or peptide-like compounds. Natural or synthetic smallmolecules which bind to BR43x2 polypeptides and prevent signaling arealso contemplated as antagonists. As such, BR43x2 antagonists would beuseful as therapeutics for treating certain disorders where blockingsignal from either a BR43x2 receptor or ligand would be beneficial.Antagonists are useful as research reagents for characterizingligand-receptor interaction. BR43x2 is expressed on transformed B celllines including EBV induced and spontaneous Burkitt's lymphoma andseveral B cell myelomas. Inhibiting the function of BR43x2 would beuseful in the treatment of B cell lymphomas or multiple myelomas. BR43x2antagonists, such as BR43x2 soluble receptors or antibodies, could beused therapeutically to mediate tumor progression.

The activity of agonists and antagonists can be determined by activityassays which determine the potency of receptor/ligand engagement. Stablytransfected B-cell lines, such as Baf3 (a murine pre-B cell linePalacios and Steinmetz, ibid. and Mathey-Prevot et al., ibid.), whichco-express high levels of reporter gene constructs for NfKB, NFAT-1 andAP-1 were made which express BR43x2. Cell lines expressing TACI and BCMAwere also be prepared in a similar manner and in Jurkat and other Blymphoma cell lines. Ztnf4 was found to signal through the reportergenes in these constructs. Soluble BR43x2 and antibodies can be used tomeasure binding.

An in vivo approach for assaying proteins of the present inventioninvolves viral delivery systems. Exemplary viruses for this purposeinclude adenovirus, herpesvirus, vaccinia virus and adeno-associatedvirus (AAV). Adenovirus, a double-stranded DNA virus, is currently thebest studied gene transfer vector for delivery of heterologous nucleicacid (for a review, see Becker et al., Meth. Cell Biol. 43:161-89, 1994;and Douglas and Curiel, Science & Medicine 4:44-53, 1997). Theadenovirus system offers several advantages: adenovirus can (i)accommodate relatively large DNA inserts; (ii) be grown to high-titer;(iii) infect a broad range of mammalian cell types; and (iv) be usedwith a large number of available vectors containing different promoters.Also, because adenoviruses are stable in the bloodstream, they can beadministered by intravenous injection.

By deleting portions of the adenovirus genome, larger inserts (up to 7kb) of heterologous DNA can be accommodated. These inserts may beincorporated into the viral DNA by direct ligation or by homologousrecombination with a co-transfected plasmid. In an exemplary system, theessential E1 gene has been deleted from the viral vector, and the viruswill not replicate unless the E1 gene is provided by the host cell (thehuman 293 cell line is exemplary). When intravenously administered tointact animals, adenovirus primarily targets the liver. If theadenoviral delivery system has an E1 gene deletion, the virus cannotreplicate in the host cells. However, the host's tissue (e.g., liver)will express and process (and, if a signal sequence is present, secrete)the heterologous protein. Secreted proteins will enter the circulationin the highly vascularized liver, and effects on the infected animal canbe determined.

The adenovirus system can also be used for protein production in vitro.By culturing adenovirus-infected non-293 cells under conditions wherethe cells are not rapidly dividing, the cells can produce proteins forextended periods of time. For instance, BHK cells are grown toconfluence in cell factories, then exposed to the adenoviral vectorencoding the secreted protein of interest. The cells are then grownunder serum-free conditions, which allows infected cells to survive forseveral weeks without significant cell division. Alternatively,adenovirus vector infected 293S cells can be grown in suspension cultureat relatively high cell density to produce significant amounts ofprotein (see Garnier et al., Cytotechnol. 15:145-55, 1994). With eitherprotocol, an expressed, secreted heterologous protein can be repeatedlyisolated from the cell culture supernatant. Within the infected 293Scell production protocol, non-secreted proteins may also be effectivelyobtained.

Well established animal models are available to test in vivo efficacy ofsoluble BR43x2, TACI, or BCMA polypeptides of the present invention incertain disease states. In particular, soluble BR43x2, TACI, or BCMApolypeptides and polypeptide fragments can be tested in vivo in a numberof animal models of autoimmune disease, such as MRL-lpr/lpr or NZB×NZWF1 congenic mouse strains which serve as a model of SLE (systemic lupuserythematosus). Such animal models are known in the art, see for exampleAutoimmune Disease Models A Guidebook, Cohen and Miller eds. AcademicPress. Offspring of a cross between New Zealand Black (NZB) and NewZealand White (NZW) mice develop a spontaneous form of SLE that closelyresembles SLE in humans. The offspring mice, known as NZBW begin todevelop IgM autoantibodies against T-cells at 1 month of age, and by 5-7months of age, Ig anti-DNA autoantibodies are the dominantimmunoglobulin. Polyclonal B-cell hyperactivity leads to overproductionof autoantibodies. The deposition of these autoantibodies, particularlyones directed against single stranded DNA is associated with thedevelopment of glomerulonephritis, which manifests clinically asproteinuria, azotemia, and death from renal failure. Kidney failure isthe leading cause of death in mice affected with spontaneous SLE, and inthe NZBW strain, this process is chronic and obliterative. The diseaseis more rapid and severe in females than males, with mean survival ofonly 245 days as compared to 406 days for the males. While many of thefemale mice will be symptomatic (proteinuria) by 7-9 months of age, somecan be much younger or older when they develop symptoms. The fatalimmune nephritis seen in the NZBW mice is very similar to theglomerulonephritis seen in human SLE, making this spontaneous murinemodel very attractive for testing of potential SLE therapeutics(Putterman and Naparstek, Murine Models of Spontaneous Systemic LupusErythematosus, Autoimmune Disease Models: A Guidebook, chapter 14, pp.217-34, 1994; Mohan et al., J. Immunol. 154:1470-80, 1995; and Daikh etal., J. Immunol. 159:3104-08, 1997). Administration of soluble TACI-IG,BR43x2-Ig, BCMA-Ig or other soluble and fusion proteins to these mice toevaluate the efficacy of TACI, BR43x2, or BCMA to amelioration ofsymptoms and alterations to the course of disease is described below inthe Example section.

Mouse models for experimental allergic encephalomyelitis (EAE) has beenused as a tool to investigate both the mechanisms of immune-mediateddisease, and methods of potential therapeutic intervention. The modelresembles human multiple sclerosis, and produces demyelination as aresult of T-cell activation to neuroproteins such as myelin basicprotein (MBP), or proteolipid protein (PLP). Inoculation with antigenleads to induction of CD4+, class II MHC-restricted T-cells (Th1).Changes in the protocol for EAE can produce acute, chronic-relapsing, orpassive-transfer variants of the model (Weinberg et al., J. Immunol.162:1818-26, 1999; Mijaba et al., Cell. Immunol. 186:94-102, 1999; andGlabinski, Meth. Enzym. 288:182-90, 1997). Administration of solubleTACI-IG, BR43x2-Ig, BCMA-Ig or other soluble and fusion proteins tothese mice to evaluate the efficacy of TACI, BR43x2, or BCMA toamelioration of symptoms and alterations to the course of disease isdescribed below in the Example section.

In the collagen-induced arthritis (CIA) model, mice develop chronicinflammatory arthritis which closely resembles human rheumatoidarthritis (RA). Since CIA shares similar immunological and pathologicalfeatures with RA, this makes it an ideal model for screening potentialhuman anti-inflammatory compounds. Another advantage in using the CIAmodel is that the mechanisms of pathogenesis are known. The T and B cellepitopes on type II collagen have been identified, and variousimmunological (delayed-type hypersensitivity and anti-collagen antibody)and inflammatory (cytokines, chemokines, and matrix-degrading enzymes)parameters relating to immune-mediating arthritis have been determined,and can be used to assess test compound efficacy in the models (Wooley,Curr. Opin. Rheum. 3:407-20, 1999; Williams et al., Immunol.89:9784-788, 1992; Myers et al., Life Sci. 61:1861-78, 1997; and Wang etal., Immunol. 92:8955-959, 1995). Administration of soluble TACI-IG,BR43x2-Ig, BCMA-Ig or other soluble and fusion proteins to these mice toevaluate the efficacy of TACI, BR43x2, or BCMA to amelioration ofsymptoms and alterations to the course of disease is described below inthe Example section.

Models for bronchial infection, such as asthma, can be created when miceare injected with ovalbumin and restimulated nasally with antigen whichproduces an asthmatic response in the bronchi similar to asthma.Administration of soluble TACI-Ig, BR43x2-Ig, BCMA-Ig, or other solubleand fusion proteins to these mice to evaluate the efficacy of TACI,BR43x2, or BCMA to amelioration of symptoms and alterations to thecourse of disease is described below in the Example section.

Myasthenia gravis (MG) is another autoimmune disease for which murinemodels are available. MG is a disorder of neuromuscular transmissioninvolving the production of autoantibodies directed against thenicotinic acetylcholine receptor (AChR). MG is acquired or inheritedwith clinical features including abnormal weakness and fatigue onexertion.

A mouse model of MG have been established. (Christadoss et al.,Establishment of a Mouse Model of Myasthenia gravis Which Mimics HumanMyasthenia gravid Pathogenesis for Immune Intervention, in Immunobiologyof Proteins and Peptides VIII, Atassi and Bixler, eds., 1995, pp.195-99.) Experimental autoimmune myasthenia gravis (EAMG) is an antibodymediated disease characterized by the presence of antibodies to AChR.These antibodies destroy the receptor leading to defective neuromuscularelectrical impulses, resulting in muscle weakness. In the EAMG model,mice are immunized with the nicotinic acetylcholine receptor. Clinicalsigns of MG become evident weeks after the second immunization. EAMG isevaluated by several methods including measuring serum levels of AChRantibodies by radioimmunoassay (Christadoss and Dauphinee, J. Immunol.136:2437-40, 1986; and Lindstrom et al., Methods Enzymol. 74:432-60,1981), measuring muscle AChR, or electromyography (Wu et al. Protocolsin Immunology. Vol. 3, Eds. Coligen, Kruisbeak, Margulies, Shevach, andStrober. John Wiley and Sons, New York, p. 15.8.1, 1997).

Another use for in vivo models includes delivery of an antigen challengeto the animal followed by administration of soluble BR43x2 (TACI) or itsligand ztnf4 and measuring the T and B cell response.

T cell dependent and T cell independent immune response can be measuredas described in Perez-Melgosa et al., J. Immunol. 163:1123-7, 1999.

Immune response in animals subjected to a regular antigen challenge (forexample, ovalbumin or collagen) followed by administration of BR43x2,TACI or BCMA polypeptides or soluble Ig-fusions can be done to measureeffect on B cell response.

Pharmacokinetic studies can be used in association with radiolabeled,soluble BR43x2, TACI or BCMA polypeptides or fusions to determine thedistribution and half life of such polypeptides in vivo. Additionallyanimal models can be used to determine the effects of soluble BR43x2,TACI or BCMA on tumors and tumor development in vivo.

Also provided is the use of BR43x2, TACI or BCMA polypeptides assurrogate markers for autoimmune diseases, kidney diseases, B and T celldiseases. Such patients can be bled and BR43x2, TACI or BCMA solublereceptors and their ligands can be detected in the blood.

The invention also provides antibodies. Antibodies to BR43x2 or peptideshaving an amino acid sequence of SEQ ID NO:8, can be obtained, forexample, using as an antigen the product of an expression vectorcontaining the polypeptide of interest, or a polypeptide isolated from anatural source. Particularly useful antibodies “bind specifically” withBR43x2 or peptides having an amino acid sequence of SEQ ID NO:10.Antibodies are considered to be specifically binding if the antibodiesbind to a BR43x2 polypeptide or a polypeptide of SEQ ID NO:8, peptide orepitope with a binding affinity (K_(a)) of 10⁶M⁻¹ or greater, preferably10⁷M⁻¹ or greater, more preferably 10⁸M⁻¹ or greater, and mostpreferably 10⁹M⁻¹ or greater. The binding affinity of an antibody can bereadily determined by one of ordinary skill in the art, for example, byScatchard analysis (Scatchard, Ann. NY Acad. Sci. 51:660, 1949).Suitable antibodies include antibodies that bind with BR43x2, inparticular the extracellular domain of BR43x2 (amino acid residues 1-120of SEQ ID NO:2) and those that bind with polypeptides having an aminoacid sequence of SEQ ID NO:10.

Anti-BR43x2 antibodies can be produced using antigenic BR43x2epitope-bearing peptides and polypeptides. Antigenic epitope-bearingpeptides and polypeptides of the present invention contain a sequence ofat least nine, preferably between 15 to about 30 amino acids containedwithin SEQ ID NO:2. However, peptides or polypeptides comprising alarger portion of an amino acid sequence of the invention, containingfrom 30 to 50 amino acids, or any length up to and including the entireamino acid sequence of a polypeptide of the invention, also are usefulfor inducing antibodies that bind with BR43x2. It is desirable that theamino acid sequence of the epitope-bearing peptide is selected toprovide substantial solubility in aqueous solvents (i.e., the sequenceincludes relatively hydrophilic residues, while hydrophobic residues arepreferably avoided). Hydrophilic peptides can be predicted by one ofskill in the art from a hydrophobicity plot, see for example, Hopp andWoods (Proc. Nat. Acad. Sci. USA 78:3824-8, 1981) and Kyte and Doolittle(J. Mol. Biol. 157: 105-142, 1982). Moreover, amino acid sequencescontaining proline residues may be also be desirable for antibodyproduction.

Polyclonal antibodies to recombinant BR43x2 protein or to BR43x2isolated from natural sources can be prepared using methods well-knownto those of skill in the art. See, for example, Green et al.,“Production of Polyclonal Antisera,” in Immunochemical Protocols(Manson, ed.), pages 1-5 (Humana Press 1992), and Williams et al.,“Expression of foreign proteins in E. coli using plasmid vectors andpurification of specific polyclonal antibodies,” in DNA Cloning 2:Expression Systems, 2nd Edition, Glover et al. (eds.), page 15 (OxfordUniversity Press 1995). The immunogenicity of a BR43x2 polypeptide canbe increased through the use of an adjuvant, such as alum (aluminumhydroxide) or Freund's complete or incomplete adjuvant. Polypeptidesuseful for immunization also include fusion polypeptides, such asfusions of BR43x2 or a portion thereof with an immunoglobulinpolypeptide or with maltose binding protein. The polypeptide immunogenmay be a full-length molecule or a portion thereof. If the polypeptideportion is “hapten-like,” such portion may be advantageously joined orlinked to a macromolecular carrier (such as keyhole limpet hemocyanin(KLH), bovine serum albumin (BSA) or tetanus toxoid) for immunization.

Although polyclonal antibodies are typically raised in animals such ashorses, cows, dogs, chicken, rats, mice, rabbits, hamsters, guinea pigs,goats or sheep, an anti-BR43x2 antibody of the present invention mayalso be derived from a subhuman primate antibody. General techniques forraising diagnostically and therapeutically useful antibodies in baboonsmay be found, for example, in Goldenberg et al., international patentpublication No. WO 91/11465, and in Losman et al., Int. J. Cancer46:310, 1990. Antibodies can also be raised in transgenic animals suchas transgenic sheep, cows, goats or pigs, and may be expressed in yeastand fungi in modified forms as will as in mammalian and insect cells.

Alternatively, monoclonal anti-BR43X2 antibodies can be generated.Rodent monoclonal antibodies to specific antigens may be obtained bymethods known to those skilled in the art (see, for example, Kohler etal., Nature 256:495, 1975, Coligan et al. (eds.), Current Protocols inImmunology, Vol. 1, pages 2.5.1-2.6.7 (John Wiley & Sons 1991), Picksleyet al., “Production of monoclonal antibodies against proteins expressedin E. coli,” in DNA Cloning 2: Expression Systems, 2nd Edition, Gloveret al. (eds.), page 93 (Oxford University Press 1995)).

Briefly, monoclonal antibodies can be obtained by injecting mice with acomposition comprising a BR43x2 gene product, verifying the presence ofantibody production by removing a serum sample, removing the spleen toobtain B-lymphocytes, fusing the B-lymphocytes with myeloma cells toproduce hybridomas, cloning the hybridomas, selecting positive cloneswhich produce antibodies to the antigen, culturing the clones thatproduce antibodies to the antigen, and isolating the antibodies from thehybridoma cultures.

In addition, an anti-BR43x2 antibody of the present invention may bederived from a human monoclonal antibody. Human monoclonal antibodiesare obtained from transgenic mice that have been engineered to producespecific human antibodies in response to antigenic challenge. In thistechnique, elements of the human heavy and light chain locus areintroduced into strains of mice derived from embryonic stem cell linesthat contain targeted disruptions of the endogenous heavy chain andlight chain loci. The transgenic mice can synthesize human antibodiesspecific for human antigens, and the mice can be used to produce humanantibody-secreting hybridomas. Methods for obtaining human antibodiesfrom transgenic mice are described, for example, by Green et al., Nat.Genet. 7:13, 1994, Lonberg et al., Nature 368:856, 1994, and Taylor etal., Int. Immun. 6:579, 1994.

Monoclonal antibodies can be isolated and purified from hybridomacultures by a variety of well-established techniques. Such isolationtechniques include affinity chromatography with Protein-A Sepharose,size-exclusion chromatography, and ion-exchange chromatography (see, forexample, Coligan at pages 2.7.1-2.7.12 and pages 2.9.1-2.9.3; Baines etal., “Purification of Immunoglobulin G (IgG),” in Methods in MolecularBiology, Vol. 10, pages 79-104 (The Humana Press, Inc. 1992)).

For particular uses, it may be desirable to prepare fragments ofanti-BR43x2 antibodies. Such antibody fragments can be obtained, forexample, by proteolytic hydrolysis of the antibody. Antibody fragmentscan be obtained by pepsin or papain digestion of whole antibodies byconventional methods. As an illustration, antibody fragments can beproduced by enzymatic cleavage of antibodies with pepsin to provide a 5Sfragment denoted F(ab′)₂. This fragment can be further cleaved using athiol reducing agent to produce 3.5S Fab′ monovalent fragments.Optionally, the cleavage reaction can be performed using a blockinggroup for the sulfhydryl groups that result from cleavage of disulfidelinkages. As an alternative, an enzymatic cleavage using pepsin producestwo monovalent Fab fragments and an Fc fragment directly. These methodsare described, for example, by Goldenberg, U.S. Pat. No. 4,331,647,Nisonoff et al., Arch Biochem. Biophys. 89:230, 1960, Porter, Biochem.J. 73:119, 1959, Edelman et al., in Methods in Enzymology Vol. 1, page422 (Academic Press 1967), and by Coligan, ibid.

Other methods of cleaving antibodies, such as separation of heavy chainsto form monovalent light-heavy chain fragments, further cleavage offragments, or other enzymatic, chemical or genetic techniques may alsobe used, so long as the fragments bind to the antigen that is recognizedby the intact antibody.

For example, Fv fragments comprise an association of V_(H) and V_(L)chains. This association can be noncovalent, as described by Inbar etal., Proc. Natl. Acad. Sci. USA 69:2659, 1972. Alternatively, thevariable chains can be linked by an intermolecular disulfide bond orcross-linked by chemicals such as gluteraldehyde (see, for example,Sandhu, Crit. Rev. Biotech. 12:437, 1992).

The Fv fragments may comprise V_(H) and V_(L) chains which are connectedby a peptide linker. These single-chain antigen binding proteins (scFv)are prepared by constructing a structural gene comprising DNA sequencesencoding the V_(H) and V_(L) domains which are connected by anoligonucleotide. The structural gene is inserted into an expressionvector which is subsequently introduced into a host cell, such as E.coli. The recombinant host cells synthesize a single polypeptide chainwith a linker peptide bridging the two V domains. Methods for producingscFvs are described, for example, by Whitlow et al., Methods: ACompanion to Methods in Enzymology 2:97, 1991, also see, Bird et al.,Science 242:423, 1988, Ladner et al., U.S. Pat. No. 4,946,778, Pack etal., Bio/Technology 11:1271, 1993, and Sandhu, ibid.

As an illustration, a scFV can be obtained by exposing lymphocytes toBR43x2 polypeptide in vitro, and selecting antibody display libraries inphage or similar vectors (for instance, through use of immobilized orlabeled BR43x2 protein or peptide). Genes encoding polypeptides havingpotential BR43x2 polypeptide binding domains can be obtained byscreening random peptide libraries displayed on phage (phage display) oron bacteria, such as E. coli. Nucleotide sequences encoding thepolypeptides can be obtained in a number of ways, such as through randommutagenesis and random polynucleotide synthesis. These random peptidedisplay libraries can be used to screen for peptides which interact witha known target which can be a protein or polypeptide, such as a ligandor receptor, a biological or synthetic macromolecule, or organic orinorganic substances. Techniques for creating and screening such randompeptide display libraries are known in the art (Ladner et al., U.S. Pat.No. 5,223,409, Ladner et al., U.S. Pat. No. 4,946,778, Ladner et al.,U.S. Pat. No. 5,403,484, Ladner et al., U.S. Pat. No. 5,571,698, and Kayet al., Phage Display of Peptides and Proteins (Academic Press, Inc.1996)) and random peptide display libraries and kits for screening suchlibraries are available commercially, for instance from Clontech (PaloAlto, Calif.), Invitrogen Inc. (San Diego, Calif.), New England Biolabs,Inc. (Beverly, Mass.), and Pharmacia LKB Biotechnology Inc. (Piscataway,N.J.). Random peptide display libraries can be screened using the BR43x2sequences disclosed herein to identify proteins which bind to BR43x2.

Another form of an antibody fragment is a peptide coding for a singlecomplementarity-determining region (CDR). CDR peptides (“minimalrecognition units”) can be obtained by constructing genes encoding theCDR of an antibody of interest. Such genes are prepared, for example, byusing the polymerase chain reaction to synthesize the variable regionfrom RNA of antibody-producing cells (see, for example, Larrick et al.,Methods: A Companion to Methods in Enzymology 2:106, 1991),Courtenay-Luck, “Genetic Manipulation of Monoclonal Antibodies,” inMonoclonal Antibodies: Production, Engineering and Clinical Application,Ritter et al. (eds.), page 166 (Cambridge University Press 1995), andWard et al., “Genetic Manipulation and Expression of Antibodies,” inMonoclonal Antibodies: Principles and Applications, Birch et al.,(eds.), page 137 (Wiley-Liss, Inc. 1995)).

Alternatively, an anti-BR43x2 antibody may be derived from a “humanized”monoclonal antibody. Humanized monoclonal antibodies are produced bytransferring mouse complementary determining regions from heavy andlight variable chains of the mouse immunoglobulin into a human variabledomain. Typical residues of human antibodies are then substituted in theframework regions of the murine counterparts. The use of antibodycomponents derived from humanized monoclonal antibodies obviatespotential problems associated with the immunogenicity of murine constantregions. General techniques for cloning murine immunoglobulin variabledomains are described, for example, by Orlandi et al., Proc. Natl. Acad.Sci. USA 86:3833, 1989. Techniques for producing humanized monoclonalantibodies are described, for example, by Jones et al., Nature 321:522,1986, Carter et al., Proc. Nat. Acad. Sci. USA 89:4285, 1992, Sandhu,Crit. Rev. Biotech. 12:437, 1992, Singer et al., J. Immun. 150:2844,1993, Sudhir (ed.), Antibody Engineering Protocols (Humana Press, Inc.1995), Kelley, “Engineering Therapeutic Antibodies,” in ProteinEngineering: Principles and Practice, Cleland et al. (eds.), pages399-434 (John Wiley & Sons, Inc. 1996), and by Queen et al., U.S. Pat.No. 5,693,762 (1997).

Polyclonal anti-idiotype antibodies can be prepared by immunizinganimals with anti-BR43x2 antibodies or antibody fragments, usingstandard techniques. See, for example, Green et al., “Production ofPolyclonal Antisera,” in Methods In Molecular Biology: ImmunochemicalProtocols, Manson (ed.), pages 1-12 (Humana Press 1992). Also, seeColigan, ibid. at pages 2.4.1-2.4.7. Alternatively, monoclonalanti-idiotype antibodies can be prepared using anti-BR43x2 antibodies orantibody fragments as immunogens with the techniques, described above.As another alternative, humanized anti-idiotype antibodies or subhumanprimate anti-idiotype antibodies can be prepared using theabove-described techniques. Methods for producing anti-idiotypeantibodies are described, for example, by Irie, U.S. Pat. No. 5,208,146,Greene, et. al., U.S. Pat. No. 5,637,677, and Varthakavi and Minocha, J.Gen. Virol. 77:1875, 1996.

Antibodies or polypeptides herein can also be directly or indirectlyconjugated to drugs, toxins, radionuclides and the like, and theseconjugates used for in vivo diagnostic or therapeutic applications. Forinstance, polypeptides or antibodies of the present invention can beused to identify or treat tissues or organs that express a correspondinganti-complementary molecule (receptor or antigen, respectively, forinstance). More specifically, BR43x2 polypeptides or anti-BR43x2antibodies, or bioactive fragments or portions thereof, can be coupledto detectable or cytotoxic molecules and delivered to a mammal havingcells, tissues or organs that express the anti-complementary molecule.

Suitable detectable molecules may be directly or indirectly attached tothe polypeptide or antibody, and include radionuclides, enzymes,substrates, cofactors, inhibitors, fluorescent markers, chemiluminescentmarkers, magnetic particles and the like. Suitable cytotoxic moleculesmay be directly or indirectly attached to the polypeptide or antibody,and include bacterial or plant toxins (for instance, diphtheria toxin,Pseudomonas exotoxin, ricin, abrin and the like), as well as therapeuticradionuclides, such as iodine-131, rhenium-188 or yttrium-90 (eitherdirectly attached to the polypeptide or antibody, or indirectly attachedthrough means of a chelating moiety, for instance). Polypeptides orantibodies may also be conjugated to cytotoxic drugs, such asadriamycin. For indirect attachment of a detectable or cytotoxicmolecule, the detectable or cytotoxic molecule can be conjugated with amember of a complementary/anticomplementary pair, where the other memberis bound to the polypeptide or antibody portion. For these purposes,biotin/streptavidin is an exemplary complementary/anticomplementarypair.

Soluble BR43x2 polypeptides or antibodies to BR43x2 can be directly orindirectly conjugated to drugs, toxins, radionuclides and the like, andthese conjugates used for in vivo diagnostic or therapeuticapplications. For instance, polypeptides or antibodies of the presentinvention can be used to identify or treat tissues or organs thatexpress a corresponding anti-complementary molecule (receptor orantigen, respectively, for instance). More specifically, BR43x2polypeptides or anti-BR43x2 antibodies, or bioactive fragments orportions thereof, can be coupled to detectable or cytotoxic moleculesand delivered to a mammal having cells, tissues or organs that expressthe anti-complementary molecule.

Suitable detectable molecules can be directly or indirectly attached tothe polypeptide or antibody, and include radionuclides, enzymes,substrates, cofactors, inhibitors, fluorescent markers, chemiluminescentmarkers, magnetic particles and the like. Suitable cytotoxic moleculescan be directly or indirectly attached to the polypeptide or antibody,and include bacterial or plant toxins (for instance, diphtheria toxin,Pseudomonas exotoxin, ricin, abrin and the like), as well as therapeuticradionuclides, such as iodine-131, rhenium-188 or yttrium-90 (eitherdirectly attached to the polypeptide or antibody, or indirectly attachedthrough means of a chelating moiety, for instance). Polypeptides orantibodies can also be conjugated to cytotoxic drugs, such asadriamycin. For indirect attachment of a detectable or cytotoxicmolecule, the detectable or cytotoxic molecule can be conjugated with amember of a complementary/anticomplementary pair, where the other memberis bound to the polypeptide or antibody portion. For these purposes,biotin/streptavidin is an exemplary complementary/anticomplementarypair.

Such polypeptide-toxin fusion proteins or antibody/fragment-toxin fusionproteins can be used for targeted cell or tissue inhibition or ablation(for instance, to treat cancer cells or tissues). Alternatively, if thepolypeptide has multiple functional domains (i.e., an activation domainor a ligand binding domain, plus a targeting domain), a fusion proteinincluding only the targeting domain can be suitable for directing adetectable molecule, a cytotoxic molecule or a complementary molecule toa cell or tissue type of interest. In instances where the domain onlyfusion protein includes a complementary molecule, the anti-complementarymolecule can be conjugated to a detectable or cytotoxic molecule. Suchdomain-complementary molecule fusion proteins thus represent a generictargeting vehicle for cell/tissue-specific delivery of genericanti-complementary-detectable/cytotoxic molecule conjugates. Thebioactive polypeptide or antibody conjugates described herein can bedelivered intravenously, intraarterially or intraductally, or may beintroduced locally at the intended site of action.

Antibodies can be made to soluble, BR43x2 polypeptides which are His orFLAG™ tagged. Antibodies can also be prepared to E. coli producedMBP-fusion proteins. Alternatively, such polypeptides could include afusion protein with Human Ig. In particular, antiserum containingpolypeptide antibodies to His-tagged, or FLAG™-tagged soluble BR43x2 canbe used in analysis of tissue distribution of BR43x2 byimmunohistochemistry on human or primate tissue. These soluble BR43x2polypeptides can also be used to immunize mice in order to producemonoclonal antibodies to a soluble human BR43x2 polypeptide. Monoclonalantibodies to a soluble human BR43x2 polypeptide can also be used tomimic ligand/receptor coupling, resulting in activation or inactivationof the ligand/receptor pair. For instance, it has been demonstrated thatcross-linking anti-soluble CD40 monoclonal antibodies provides astimulatory signal to B cells that have been sub-optimally activatedwith anti-IgM or LPS, and results in proliferation and immunoglobulinproduction. These same monoclonal antibodies act as antagonists whenused in solution by blocking activation of the receptor. Monoclonalantibodies to BR43x2 can be used to determine the distribution,regulation and biological interaction of the BR43x2/BR43x2-ligand pairon specific cell lineages identified by tissue distribution studies.

The invention also provides isolated and purified BR43x2, TACI and BCMApolynucleotide probes or primers. Such polynucleotide probes can be RNAor DNA. DNA can be either cDNA or genomic DNA. Polynucleotide probes aresingle or double-stranded DNA or RNA, generally syntheticoligonucleotides, but may be generated from cloned cDNA or genomicsequences and will generally comprise at least 16 nucleotides, moreoften from 17 nucleotides to 25 or more nucleotides, sometimes 40 to 60nucleotides, and in some instances a substantial portion, domain or eventhe entire BR43x2 gene or cDNA. Probes and primers are generallysynthetic oligonucleotides, but may be generated from cloned cDNA orgenomic sequences or its complements. Analytical probes will generallybe at least 20 nucleotides in length, although somewhat shorter probes(14-17 nucleotides) can be used. PCR primers are at least 5 nucleotidesin length, preferably 15 or more nt, more preferably 20-30 nt. Shortpolynucleotides can be used when a small region of the gene is targetedfor analysis. For gross analysis of genes, a polynucleotide probe maycomprise an entire exon or more. Probes can be labeled to provide adetectable signal, such as with an enzyme, biotin, a radionuclide,fluorophore, chemiluminescer, paramagnetic particle and the like, whichare commercially available from many sources, such as Molecular Probes,Inc., Eugene, Oreg., and Amersham Corp., Arlington Heights, Ill., usingtechniques that are well known in the art. Preferred regions from whichto construct probes include the ligand binding region, cysteine-richpseudo repeats, signal sequences, and the like. Techniques fordeveloping polynucleotide probes and hybridization techniques are knownin the art, see for example, Ausubel et al., eds., Current Protocols inMolecular Biology, John Wiley and Sons, Inc., NY, 1991.

BR43x2, TACI and BCMA polypeptides and antibodies may be used withindiagnostic systems to detect the presence of BR43x2, TACI, and BCMA andBR43x2, TACI, and BCMA ligand polypeptides, such as ztnf4. Theinformation derived from such detection methods would provide insightinto the significance of BR43x2 polypeptides in various diseases, and asa would serve as diagnostic tools for diseases for which altered levelsof BR43x2 are significant. Altered levels of BR43x2, TACI and BCMAreceptor polypeptides may be indicative of pathological conditionsincluding cancer, autoimmune disorders and infectious diseases.

In a basic assay, a single-stranded probe molecule is incubated withRNA, isolated from a biological sample, under conditions of temperatureand ionic strength that promote base pairing between the probe andtarget BR43x2, TACI or BCMA RNA species. After separating unbound probefrom hybridized molecules, the amount of hybrids is detected.

Well-established hybridization methods of RNA detection include northernanalysis and dot/slot blot hybridization (see, for example, Ausubelibid. and Wu et al. (eds.), “Analysis of Gene Expression at the RNALevel,” in Methods in Gene Biotechnology, pages 225-239 (CRC Press, Inc.1997)). Nucleic acid probes can be detectably labeled with radioisotopessuch as ³²P or ³⁵S. Alternatively, BR43x2 RNA can be detected with anonradioactive hybridization method (see, for example, Isaac (ed.),Protocols for Nucleic Acid Analysis by Nonradioactive Probes, HumanaPress, Inc., 1993). Typically, nonradioactive detection is achieved byenzymatic conversion of chromogenic or chemiluminescent substrates.Illustrative nonradioactive moieties include biotin, fluorescein, anddigoxigenin.

BR43x2, TACI, and BCMA oligonucleotide probes are also useful for invivo diagnosis. As an illustration, ¹⁸F-labeled oligonucleotides can beadministered to a subject and visualized by positron emission tomography(Tavitian et al., Nature Medicine 4:467, 1998).

Numerous diagnostic procedures take advantage of the polymerase chainreaction (PCR) to increase sensitivity of detection methods. Standardtechniques for performing PCR are well-known (see, generally, Mathew(ed.), Protocols in Human Molecular Genetics (Humana Press, Inc. 1991),White (ed.), PCR Protocols: Current Methods and Applications (HumanaPress, Inc. 1993), Cotter (ed.), Molecular Diagnosis of Cancer (HumanaPress, Inc. 1996), Hanausek and Walaszek (eds.), Tumor Marker Protocols(Humana Press, Inc. 1998), Lo (ed.), Clinical Applications of PCR(Humana Press, Inc. 1998), and Meltzer (ed.), PCR in Bioanalysis (HumanaPress, Inc. 1998)). PCR primers can be designed to amplify a sequenceencoding a particular BR43x2 domain or motif, such as the BR43x2, TACIor BCMA cysteine rich pseudo repeat.

One variation of PCR for diagnostic assays is reverse transcriptase-PCR(RT-PCR). In the RT-PCR technique, RNA is isolated from a biologicalsample, reverse transcribed to cDNA, and the cDNA is incubated withBR43x2 primers (see, for example, Wu et al. (eds.), “Rapid Isolation ofSpecific cDNAs or Genes by PCR,” in Methods in Gene Biotechnology, CRCPress, Inc., pages 15-28, 1997). PCR is then performed and the productsare analyzed using standard techniques.

As an illustration, RNA is isolated from biological sample using, forexample, the guanidinium-thiocyanate cell lysis procedure describedabove. Alternatively, a solid-phase technique can be used to isolatemRNA from a cell lysate. A reverse transcription reaction can be primedwith the isolated RNA using random oligonucleotides, short homopolymersof dT, or BR43x2, TACI, or BCMA anti-sense oligomers. Oligo-dT primersoffer the advantage that various mRNA nucleotide sequences are amplifiedthat can provide control target sequences. BR43x2, TACI, or BCMAsequences are amplified by the polymerase chain reaction using twoflanking oligonucleotide primers that are typically at least 5 bases inlength.

PCR amplification products can be detected using a variety ofapproaches. For example, PCR products can be fractionated by gelelectrophoresis, and visualized by ethidium bromide staining.Alternatively, fractionated PCR products can be transferred to amembrane, hybridized with a detectably-labeled BR43x2 probe, andexamined by autoradiography. Additional alternative approaches includethe use of digoxigenin-labeled deoxyribonucleic acid triphosphates toprovide chemiluminescence detection, and the C-TRAK colorimetric assay.

Another approach is real time quantitative PCR (Perkin-Elmer Cetus,Norwalk, Conn.). A fluorogenic probe, consisting of an oligonucleotidewith both a reporter and a quencher dye attached, anneals specificallybetween the forward and reverse primers. Using the 5′ endonucleaseactivity of Taq DNA polymerase, the reporter dye is separated from thequencher dye and a sequence-specific signal is generated and increasesas amplification increases. The fluorescence intensity can becontinuously monitored and quantified during the PCR reaction.

Another approach for detection of BR43x2, TACI, or BCMA expression iscycling probe technology (CPT), in which a single-stranded DNA targetbinds with an excess of DNA-RNA-DNA chimeric probe to form a complex,the RNA portion is cleaved with RNase H, and the presence of cleavedchimeric probe is detected (see, for example, Beggs et al., J. Clin.Microbiol. 34:2985, 1996 and Bekkaoui et al., Biotechniques 20:240,1996). Alternative methods for detection of BR43x2, TACI or BCMAsequences can utilize approaches such as nucleic acid sequence-basedamplification (NASBA), cooperative amplification of templates bycross-hybridization (CATCH), and the ligase chain reaction (LCR) (see,for example, Marshall et al., U.S. Pat. No. 5,686,272 (1997), Dyer etal., J. Virol. Methods 60:161, 1996; Ehricht et al., Eur. J. Biochem.243:358, 1997 and Chadwick et al., J. Virol. Methods 70:59, 1998). Otherstandard methods are known to those of skill in the art.

BR43x2, TACI, and BCMA probes and primers can also be used to detect andto localize BR43x2, TACI, or BCMA gene expression in tissue samples.Methods for such in situ hybridization are well-known to those of skillin the art (see, for example, Choo (ed.), In Situ HybridizationProtocols, Humana Press, Inc., 1994; Wu et al. (eds.), “Analysis ofCellular DNA or Abundance of mRNA by Radioactive In Situ Hybridization(RISH),” in Methods in Gene Biotechnology, CRC Press, Inc., pages259-278, 1997 and Wu et al. (eds.), “Localization of DNA or Abundance ofmRNA by Fluorescence In Situ Hybridization (RISH),” in Methods in GeneBiotechnology, CRC Press, Inc., pages 279-289, 1997).

Various additional diagnostic approaches are well-known to those ofskill in the art (see, for example, Mathew (ed.), Protocols in HumanMolecular Genetics Humana Press, Inc., 1991; Coleman and Tsongalis,Molecular Diagnostics, Humana Press, Inc., 1996 and Elles, MolecularDiagnosis of Genetic Diseases, Humana Press, Inc., 1996).

In addition, such polynucleotide probes could be used to hybridize tocounterpart sequences on individual chromosomes. Chromosomalidentification and/or mapping of the BR43x2 gene could provide usefulinformation about gene function and disease association. Many mappingtechniques are available to one skilled in the art, for example, mappingsomatic cell hybrids, and fluorescence in situ hybridization (FISH). Apreferred method is radiation hybrid mapping. Radiation hybrid mappingis a somatic cell genetic technique developed for constructinghigh-resolution, contiguous maps of mammalian chromosomes (Cox et al.,Science 250:245-50, 1990). Partial or full knowledge of a gene'ssequence allows the designing of PCR primers suitable for use withchromosomal radiation hybrid mapping panels. Commercially availableradiation hybrid mapping panels which cover the entire human genome,such as the Stanford G3 RH Panel and the GeneBridge 4 RH Panel (ResearchGenetics, Inc., Huntsville, Ala.), are available. These panels enablerapid, PCR based, chromosomal localizations and ordering of genes,sequence-tagged sites (STSs), and other non-polymorphic- and polymorphicmarkers within a region of interest. This includes establishing directlyproportional physical distances between newly discovered genes ofinterest and previously mapped markers. The precise knowledge of agene's position can be useful in a number of ways including: 1)determining if a sequence is part of an existing contig and obtainingadditional surrounding genetic sequences in various forms such as YAC-,BAC- or cDNA clones, 2) providing a possible candidate gene for aninheritable disease which shows linkage to the same chromosomal region,and 3) for cross-referencing model organisms such as mouse which may bebeneficial in helping to determine what function a particular gene mighthave.

Chromosomal localization can also be done using STSs. An STS is a DNAsequence that is unique in the human genome and can be used as areference point for a particular chromosome or region of a chromosome.An STS can be defined by a pair of oligonucleotide primers that can beused in a polymerase chain reaction to specifically detect this site inthe presence of all other genomic sequences. Since STSs are based solelyon DNA sequence they can be completely described within a database, forexample, Database of Sequence Tagged Sites (dbSTS), GenBank, (NationalCenter for Biological Information, National Institutes of Health,Bethesda, Md. http://www.ncbi.nlm.nih.gov), they can be searched with agene sequence of interest for the mapping data contained within theseshort genomic landmark STS sequences.

The present invention also provides reagents for additional diagnosticapplications. For example, the BR43x2 gene, a probe comprising BR43x2DNA or RNA, or a subsequence thereof can be used to determine if theBR43x2 gene is present on a particular chromosome or if a mutation hasoccurred. Detectable chromosomal aberrations at the BR43x2 gene locusinclude, but are not limited to, aneuploidy, gene copy number changes,insertions, deletions, restriction site changes and rearrangements.These aberrations can occur within the coding sequence, within introns,or within flanking sequences, including upstream promoter and regulatoryregions, and may be manifested as physical alterations within a codingsequence or changes in gene expression level.

In general, these diagnostic methods comprise the steps of (a) obtaininga genetic sample from a patient; (b) incubating the genetic sample witha polynucleotide probe or primer as disclosed above, under conditionswherein the polynucleotide will hybridize to complementarypolynucleotide sequence, to produce a first reaction product; and (iii)comparing the first reaction product to a control reaction product. Adifference between the first reaction product and the control reactionproduct is indicative of a genetic abnormality in the patient. Geneticsamples for use within the present invention include genomic DNA, cDNA,and RNA. The polynucleotide probe or primer can be RNA or DNA, and willcomprise a portion of SEQ ID NO:3, the complement of SEQ ID NO:1, or anRNA equivalent thereof. Suitable assay methods in this regard includemolecular genetic techniques known to those in the art, such asrestriction fragment length polymorphism (RFLP) analysis, short tandemrepeat (STR) analysis employing PCR techniques, ligation chain reaction(Barany, PCR Methods and Applications 1:5-16, 1991), ribonucleaseprotection assays, and other genetic linkage analysis techniques knownin the art (Sambrook et al., ibid.; Ausubel et. al., ibid.; Marian,Chest 108:255-65, 1995). Ribonuclease protection assays (see, e.g.,Ausubel et al., ibid., ch. 4) comprise the hybridization of an RNA probeto a patient RNA sample, after which the reaction product (RNA-RNAhybrid) is exposed to RNase. Hybridized regions of the RNA are protectedfrom digestion. Within PCR assays, a patient's genetic sample isincubated with a pair of polynucleotide primers, and the region betweenthe primers is amplified and recovered. Changes in size or amount ofrecovered product are indicative of mutations in the patient. AnotherPCR-based technique that can be employed is single strand conformationalpolymorphism (SSCP) analysis (Hayashi, PCR Methods and Applications1:34-8, 1991).

Antisense methodology can be used to inhibit BR43x2, TACI, or BCMA genetranscription, such as to inhibit B cell development and interactionwith other cells. Polynucleotides that are complementary to a segment ofa BR43x2, TACI, or BCMA-encoding polynucleotide (e.g., a polynucleotideas set forth in SEQ ID NO:3) are designed to bind to BR43x2, TACI, orBCMA-encoding mRNA and to inhibit translation of such mRNA. Suchantisense polynucleotides are used to inhibit expression of BR43x2,TACI, or BCMA polypeptide-encoding genes in cell culture or in asubject.

Mice engineered to express BR43x2, TACI, or BCMA, referred to as“transgenic mice,” and mice that exhibit a complete absence of BR43x2,TACI, or BCMA function, referred to as “knockout mice,” may also begenerated (Snouwaert et al., Science 257:1083, 1992; Lowell et al.,Nature 366:740-42, 1993; Capecchi, Science 244: 1288-92, 1989; Palmiteret al. Annu Rev Genet. 20: 465-99, 1986). For example, transgenic micethat over-express BR43x2, TACI, or BCMA either ubiquitously or under atissue-specific or tissue-restricted promoter can be used to ask whetherover-expression causes a phenotype. For example, over-expression of awild-type BR43x2, TACI, or BCMA polypeptide, polypeptide fragment or amutant thereof may alter normal cellular processes, resulting in aphenotype that identifies a tissue in which BR43x2, TACI, or BCMAexpression is functionally relevant and may indicate a therapeutictarget for BR43x2, TACI, BCMA or their agonists or antagonists. Forexample, a preferred transgenic mouse to engineer is one thatover-expresses soluble BR43x2, TACI or BCMA. Moreover, suchover-expression may result in a phenotype that shows similarity withhuman diseases. Similarly, knockout BR43x2, TACI, or BCMA mice can beused to determine where BR43x2 is absolutely required in vivo. Thephenotype of knockout mice is predictive of the in vivo effects that aBR43x2, TACI, or BCMA antagonist, such as those described herein, mayhave. The human BR43x2, TACI, or BCMA cDNA can be used to isolate murineBR43x2, TACI, or BCMA mRNA, cDNA and genomic DNA, which are subsequentlyused to generate knockout mice. These mice may be employed to study theBR43x2, TACI, or BCMA gene and the protein encoded thereby in an in vivosystem, and can be used as in vivo models for corresponding humandiseases. Moreover, transgenic expression of BR43x2, TACI, or BCMAantisense polynucleotides or ribozymes directed against BR43x2, TACI, orBCMA, described herein, can be used analogously to transgenic micedescribed above.

Pharmaceutically effective amounts of BR43x2, TACI, or BCMA polypeptidesof the present invention can be formulated with pharmaceuticallyacceptable carriers for parenteral, oral, nasal, rectal, topical,transdermal administration or the like, according to conventionalmethods. Formulations may further include one or more diluents, fillers,emulsifiers, preservatives, buffers, excipients, and the like, and maybe provided in such forms as liquids, powders, emulsions, suppositories,liposomes, transdermal patches and tablets, for example. Slow orextended-release delivery systems, including any of a number ofbiopolymers (biological-based systems), systems employing liposomes, andpolymeric delivery systems, can also be utilized with the compositionsdescribed herein to provide a continuous or long-term source of theBR43x2 polypeptide or antagonist. Such slow release systems areapplicable to formulations, for example, for oral, topical andparenteral use. The term “pharmaceutically acceptable carrier” refers toa carrier medium which does not interfere with the effectiveness of thebiological activity of the active ingredients and which is not toxic tothe host or patient. One skilled in the art may formulate the compoundsof the present invention in an appropriate manner, and in accordancewith accepted practices, such as those disclosed in Remington: TheScience and Practice of Pharmacy, Gennaro, ed., Mack Publishing Co.,Easton Pa., 19th ed., 1995.

As used herein a “pharmaceutically effective amount” of a BR43x2, TACI,or BCMA polypeptide, agonists or antagonist is an amount sufficient toinduce a desired biological result. The result can be alleviation of thesigns, symptoms, or causes of a disease, or any other desired alterationof a biological system. For example, an effective amount of a BR43x2,TACI, or BCMA polypeptide is that which provides either subjectiverelief of symptoms or an objectively identifiable improvement as notedby the clinician or other qualified observer. For example, such aneffective amount of a BR43x2, TACI, or BCMA polypeptide or solublefusion would provide a decrease in B cell response during the immuneresponse, inhibition or decrease in autoantibody production, inhibitionof diminution of symptoms associated with SLE, MG or RA. Effectiveamounts of BR43x2, TACI, or BCMA will decrease the percentage of B cellsin peripheral blood. Effective amounts of the BR43x2, TACI, or BCMApolypeptides can vary widely depending on the disease or symptom to betreated. The amount of the polypeptide to be administered and itsconcentration in the formulations, depends upon the vehicle selected,route of administration, the potency of the particular polypeptide, theclinical condition of the patient, the side effects and the stability ofthe compound in the formulation. Thus, the clinician will employ theappropriate preparation containing the appropriate concentration in theformulation, as well as the amount of formulation administered,depending upon clinical experience with the patient in question or withsimilar patients. Such amounts will depend, in part, on the particularcondition to be treated, age, weight, and general health of the patient,and other factors evident to those skilled in the art. Typically a dosewill be in the range of 0.1-100 mg/kg of subject. Doses for specificcompounds may be determined from in vitro or ex vivo studies incombination with studies on experimental animals. Concentrations ofcompounds found to be effective in vitro or ex vivo provide guidance foranimal studies, wherein doses are calculated to provide similarconcentrations at the site of action.

The invention is further illustrated by the following non-limitingexamples.

EXAMPLES Example 1 Identification of BR43x2

The TACI isoform was cloned from RPMI array library using secretion trapapproach. An RPMI 1788 (activated B-cell line) library was arrayed usingtwenty 96-well plates. Each well contained about 100 E. coli colonies,with each colony containing one cDNA clone. DNA minipreps were preparedin 96-well format using the TomTech Quadra 9600. The isolated DNA wasthen pooled into 120 pools which represent 1600 clones each. These poolswere transfected into Cos-7 cells and plated into 12-well plates. Threemicroliters of pool DNA and 5 μl LipofectAMINE were mixed in 92 μlserum-free DMEM media (55 mg sodium pyruvate, 146 mg L-glutamine, 5 mgtransferrin, 2.5 mg insulin, 1 μg selenium and 5 mg fetuin in 500 mlDMEM), incubated at room temperature for 30 minutes, followed byaddition of 400 μl serum-free DMEM media. The DNA-LipofectAMINE mix wasadded onto 220,000 Cos-7 cells/well plated on 12-well tissue cultureplates and incubated for 5 hours at 37° C. Following incubation, 500 μlof 20% FBS DMEM media (100 ml FBS, 55 mg sodium pyruvate and 146 mgL-glutamine in 500 ml DMEM) was added to each well and the cells wereincubated overnight.

The secretion trap screen was performed using biotinylated, FLAG-taggedztnf4. The cells were rinsed with PBS and fixed for 15 minutes with 1.8%formaldehyde in PBS. The cells were then washed with TNT (0.1 MTris-HCl, 0.15 M NaCl, and 0.05% Tween-20 in H₂O). Cells were permeatedwith 0.1% Triton-X in PBS for 15 minutes followed by a wash in TNT. Thecells were blocked for 1 hour with TNB (0.1 M Tris-HCl, 0.15 M NaCl and0.5% Blocking Reagent) using a NEN Renaissance® TSA-Direct Kit (NEN,Boston, Mass.) according the manufacturer's instruction. The cells werewashed with TNT and blocked for 15 minutes with avidin and then biotin(Vector Labs Cat# SP-2001) washing in-between with TNT. The cells wereincubated for 1 hour with 1 μg/ml ztnf4/Flag/Biotin in TNB followed by aTNT wash. The cells were then incubated for one hour with a 1:300dilution of streptavidin-HRP (NEN) in TNB, and washed with TNT.Hybridizations were detected with fluorescein tyramide reagent diluted1:50 in dilution buffer (NEN) and incubated for 4.4 minutes and washedwith TNT. Cells were preserved with Vectashield Mounting Media (VectorLabs, Burlingame, Calif.) diluted 1:5 in TNT.

The cells were visualized by fluorescent microscopy using a FITC filter.Twelve pools were positive for ztnf4 binding. Pool D8 (representing 1600clones) was broken down and a single clone (D8-1), positive for ztnf4binding, was isolated. Sequencing analysis revealed clone, D8-1,contained a polypeptide sequence which encoded an isoform of TACI, inwhich the Phe21-Arg67 first cysteine-rich pseudo repeat of TACI wasreplaced by a single amino acid residue, tryptophan. This isoform wasdesignated BR43x2, the polynucleotide sequence of which is presented inSEQ ID NO:1.

Example 2 Localization of BR43x1 in Lymphocytes and Monocytes

Reverse transcriptase PCR was used to localize BR43x1 expression in Tand B cells and monocytes. Oligonucleotide primers ZC19980 (SEQ IDNO:15) and ZC19981 (SEQ ID NO:16) were used to screen CD19⁺, CD3⁺ andmonocyte cDNA for BR43. The reverse transcriptase reaction was carriedout at 94° C. for 3 minutes, followed by 30 cycles at 94° C. for 30seconds, 68° C. for 2 minutes and 72° C. for 1 minute, followed by a 7minute extension at 72° C. A band of the expected size, 720 bp, wasdetected in B cells only and not in activated T cells as had beenreported for TACI using antibodies (von Bülow and Bram, ibid.).

Example 3 B cell Proliferation Assay Using the BR43 Ligand Ztnf4

A vial containing 1×10⁸ frozen, apheresed peripheral blood mononuclearcells (PBMCs) was quickly thawed in 37° C. water bath and resuspended in25 ml B cell medium (Iscove's Modified Dulbecco's Medium, 10% heatinactivated fetal bovine serum, 5% L-glutamine, 5% Pen/Strep) in a 50 mltube. Cells were tested for viability using Trypan Blue (GIBCO BRL,Gaithersburg, Md.). Ten milliliters of Ficoll/Hypaque Plus (PharmaciaLKB Biotechnology Inc., Piscataway, N.J.) was layered under cellsuspension and spun for 30 minutes at 1800 rpm and allowed to stop withthe brake off. The interphase layer was then removed and transferred toa fresh 50 ml tube, brought up to a final volume of 40 ml with PBS andspun for 10 minutes at 1200 rpm with the brake on. The viability of theisolated B cells was tested using Trypan Blue. The B cells wereresuspended at a final concentration of 1×10⁶ cells/ml in B cell mediumand plated at 180 μl/well in a 96 well U bottom plate (Falcon, VWR,Seattle, Wash.).

To the cells were added one of the following stimulators to bring thefinal volume to 200 ml/well:

Soluble, FLAG-tagged ztnf-4sCF or ztnf-4sNF, at 10 fold dilutions from 1mg-1 ng/ml either alone, with 10 μg/ml anti-IgM (goat anti Human IgM)diluted in NaH₂CO₃, ph 9.5, (Southern Biotechnology Associates, Inc.,Birmingham, Ala.); or with 10 μg/ml anti-IgM, and 10 ng/ml recombinanthuman IL4 (diluted in PBS and 0.1% BSA). Additionally, other cytokinessuch as IL-3 and IL-6 as well as a soluble CD40 (sCD40) antibody(Pharmingen, San Diego, Calif.) were tested as well. As a control thecells incubated with 0.1% bovine serum albumen (BSA) and PBS, 10 μg/mlanti-IgM or 10 μg/ml anti-IgM and 10 ng/ml IL4 (or other cytokines). Thecells were then incubated at 37° C. in a humidified incubator for 72hours. Sixteen hours prior to harvesting, 1 μCi ³H thymidine was addedto all wells. The cells were harvested into a 96 well filter plate(UniFilter GF/C, Packard, Meriden, Conn.) where they were harvestedusing a cell harvester (Packard) and collected according tomanufacturer's instructions. The plates were dried at 55° C. for 20-30minutes and the bottom of the wells were sealed with an opaque platesealer. To each well was added 0.25 ml of scintillation fluid(Microscint-O, Packard) and the plate was read using a TopCountMicroplate Scintillation Counter (Packard).

To measure induction of IgG production in response to various B cellmitogens following stimulation of purified B cells, cells were preparedas described and incubated for 9 days. The cell supernatant wascollected to determine IgG production.

To measure cell surface marker activation in response to various B cellmitogens following stimulation of purified B cells, cells were preparedas described above but incubated only 48 hours. Cell surface markerswere measured by FACS analysis.

Proliferation of human purified B cells stimulated with the various Bcell mitogens is summarized in Table 6:

TABLE 6 Stimulus Proliferative Index ztnf4 1.5 ztnf4 + IL4 9.9 ztnf4 +anti-IgM + IL4 15.8 

A synergistic affect of ztnf4 with IL4, IL3 (10 μg/ml) and IL6 (10μg/ml) was seen on B cell proliferation. A two fold increase in B cellsignaling was seen when using sCD40.

Induction of IgG production (ng/ml) in response to various B cellmitogens following stimulation of purified B cells is summarized inTable 7.

TABLE 7 Stimulus Control Ztnf4 anti-IgM  3 7.5 anti-IgM + IL-4 13 32anti-IgM + IL-4 + IL-5 10 45

An increase in cell surface activation markers after stimulation ofpurified B cells with ztnf4 alone, or with anti-IgM or anti-IgM+IL-4 wasseen. There was no effect on the proliferation of PBMNCs in the presenceof optimal or suboptimal T cell mitogens. Also, no affect on TNFαproduction was seen in purified monocytes in response to LPSstimulation.

FIG. 3 shows soluble ztnf4 co-activation of human B lymphocytes toproliferate and secrete immunoglobulin. FIG. 3A shows purified humanperipheral blood B cells proliferation in response to stimulation withsoluble ztnf4 (25 ng/ml) in the presence of IL-4 alone, and IL-4 withanti-IgM, anti-CD40, or anti-CD19, after five days in culture. FIG. 3Bshows the levels of IgM and IgG measured in the supernatants obtainedfrom human B cells stimulated with soluble ztnf4 in the presence of IL-4or IL-4+IL-5, after nine days in culture.

These results suggest that soluble ztnf4 is a B cell activation moleculewhich acts in concert with other B cell stimuli and weakly by itself.Soluble ztnf4 promotes B cell proliferation and Ig production. The upregulation of adhesion molecules, costimulatory molecules and activationreceptors suggests a role for promoting APC function of B cells.

FIG. 4 shows stimulation of human peripheral blood B cells with solubleztnf4 (25 ng/ml) or a control protein (ubiquitin) in the presence of 10ng/ml IL-4 for 5 days in vitro. Purified TACI-Ig, BCMA-Ig, or control Fcwere tested for inhibition of soluble ztnf4 specific proliferation.

Example 4 Selecting TACI and BCMA Transformed BHK Cells Using Ztnf4Binding

BHK cells expressing a high level of TACI protein were selected bydilution cloning of a transfectant pool. Transfectant cells (2×10⁵) wereincubated on ice for 30 minutes with biotinylated ztnf4 at 1 μg/ml inbinding buffer (PBS, 2% BSA, 0.02% NaN₃). Cells were washed 2× withbinding buffer, then incubated with SA-PE (Caltag) (1:1000 dilution inbinding buffer) on ice for 30 minutes. Cells were then washed 2× inbinding buffer, resuspended in binding buffer, and read by FACS (FACSVantage, Becton Dickinson). Clones with the highest binding of TNF4 areselected.

BHK cells expressing a high level of BCMA protein were selected bysurface labeling the BCMA-expressing transfectant pool with biotinylatedztnf4. This was followed by streptavidin-Phyco-Erythrin (SA-PE CaltagBurlingame, Calif.) and sterile sorting for bright cells in FL2 on theFACS Vantage (Becton Dickinson). The single colonies were then screenedfor ztnf4 binding.

Example 5 Tissue Distribution

Human Multiple Tissue Northern Blots (MTN I, MTN II and MTN III;Clontech) were probed to determine the tissue distribution of humanBR43x2 and TACI expression. An approximately 500 by PCR derived probe(SEQ ID NO:21) was amplified using BR43x2 (SEQ ID NO:1) as templates andoligonucleotide ZC20061 (SEQ ID NO:22) and ZC20062 (SEQ ID NO:23) asprimers. This sequence is identical to the homologous region of TACI.The amplification was carried out as follows: 1 cycle at 94° C. for 1.0minutes, 30 cycles of 94° C. for 30 seconds, 60° C. for 30 seconds and72° C. for 30 seconds, followed by 1 cycle at 72° C. for 10 minutes. ThePCR products were visualized by agarose gel electrophoresis and the 500by PCR product was purified using a Gel Extraction Kit (Qiagen,Chatsworth, Calif.) according to manufacturer's instructions. The probewas radioactively labeled using the MULTIPRIME DNA labeling kit(Amersham, Arlington Heights, Ill.) according to the manufacturer'sinstructions. The probe was purified using a NUCTRAP push column(Stratagene). EXPRESSHYB (Clontech) solution was used forprehybridization and as a hybridizing solution for the Northern blots.Hybridization took place overnight at 65° C. using 10⁶ cpm/ml of labeledprobe. The blots were then washed in 2×SSC and 0.1% SDS at room temp,followed by 2 washes in 0.1×SSC and 0.1% SDS at 50° C. A transcript ofapproximately 1.5 kb was detected in spleen, lymph node and smallintestine.

Human Multiple Tissue Northern Blots (MTN I, MTN II and MTN III;Clontech) were probed to determine the tissue distribution of human BCMAexpression. An approximately 257 by PCR derived probe (SEQ ID NO:24) wasamplified using Daudi cell cDNA as a template and oligonucleotideZC21065 (SEQ ID NO:25) and ZC21067 (SEQ ID NO:26) as primers. Theamplification was carried out as follows: 1 cycle at 94° C. for 1.0Minutes, 35 cycles of 94° C. for 30 seconds, 60° C. for 30 seconds and72° C. for 30 seconds, followed by 1 cycle at 72° C. for 10 minutes. ThePCR products were visualized by agarose gel electrophoresis and the 257by PCR product was purified using a Gel Extraction Kit (Qiagen,Chatsworth, Calif.) according to manufacturer's instructions. The probewas radioactively labeled using the MULTIPRIME DNA labeling kit(Amersham, Arlington Heights, Ill.) according to the manufacturer'sinstructions. The probe was purified using a NUCTRAP push column(Stratagene). EXPRESSHYB (Clontech) solution was used forprehybridization and as a hybridizing solution for the Northern blots.Hybridization took place overnight at 65° C. using 10⁶ cpm/ml of labeledprobe. The blots were then washed in 2×SSC and 0.1% SDS at room temp,followed by 2 washes in 0.1×SSC and 0.1% SDS at 50° C. A transcript ofapproximately 1.2 kb was detected in stomach, small intestine, lymphnode, trachea, spleen and testis.

RNA Master Dot Blots (Clontech) that contained RNAs from various tissuesthat were normalized to 8 housekeeping genes was also probed with eitherthe TACI probe (SEQ ID NO:21) or the BCMA probe (SEQ ID NO:24) andhybridized as described above. BR43x2/TACI expression was seen inspleen, lymph node, small intestine, stomach, salivary gland, appendix,lung, bone marrow and fetal spleen. BCMA expression was detected insmall intestine, spleen, stomach, colon, lymph node and appendix.

A human Tumor Panel Blot V (Invitrogen Inc., San Diego, Calif.) and ahuman lymphoma blot (Invitrogen) were probed as described above eitherwith a Br43x2/TACI probe (SEQ ID NO:21) or a BCMA probe (SEQ ID NO:24).A 1.5 kb transcript corresponding to TACI was found in non-Hodgkin'slymphoma and parotid tumor. A 1.2 kb transcript corresponding to BCMAwas found in adenolymphoma, non-Hodgkins lymphoma, and parotid tumor.

Total RNA from CD4+, CD8+, CD19+ and mixed lymphocyte reaction cells(CellPro, Bothell, Wash.) was prepared using guanidine isothiocyanate(Chirgwin et al., Biochemistry 18:52-94, 1979), followed by a CsClcentrifugation step. Poly(A)+ RNA was isolated using oligo d(T)cellulose chromatography (Aviv and Leder, Proc. Natl. Acad. Sci. USA.69:1408-12, 1972). Northern blot analysis was then performed as follows.

About 2 mg of each of the poly A+ RNAs was denatured in 2.2 Mformaldehyde/phosphate buffer (50 mM Na₂HPO₄, 50 mM NaH₂PO₄, 50 mMNaOAc, 1 mM EDTA and 2.2 M formaldehyde) and separated by 1.5% agarosemini gel (Stratagene Cloning Systems, La Jolla, Calif.) electrophoresisin formaldehyde/phosphate buffer. The RNA was blotted overnight onto anytran filter (Schleicher & Schuell, Keene, N.H.), and the filter was UVcrosslinked (1,200 mJoules) in a STRATALINKER® UV crosslinker(Stratagene Cloning Systems) and then baked at 80° C. for 1 hour.

The blots were probed with either a TACI (SEQ ID NO:21) or BCMA (SEQ IDNO: 24) probe. A 1.5 kb band representing TACI was detected only in CD19⁺ cells. A 1.2 kb transcript representing BCMA was detected faintly inCD 8⁺, CD 19⁺ and MLR cells.

Additional Northern Blot analysis was carried out on blots made withpoly(A) RNA from K-562 cells (erythroid, ATCC CCL 243), HUT78 cells (Tcell, ATCC TIB-161), Jurkat cells (T cell), DAUDI (Burkitt's humanlymphoma, Clontech, Palo Alto, Calif.), RAJI (Burkitt's human lymphoma,Clontech) and HL60 (Monocyte) as described above. The blots were probedwith either a TACI (SEQ ID NO:21) or BCMA (SEQ ID NO:24) probe. Atranscript of 1.5 kb corresponding to TACI was detected in Raji cells. Atranscript of 1.2 kb corresponding to BCMA was detected in Daudi, Rajiand Hut 78 cells.

A PCR-based screen was used to identify tissues which expressed human ormurine TACI and human BCMA. Human and Murine Rapid-Scan™ Gene ExpressionPanels (OriGene Technologies, Inc., Rockville, Md.), were screenedaccording to manufacturer's instructions. Oligonucleotide primersZC24200 (SEQ ID NO:27) and ZC24201 (SEQ ID NO:28) were designed to spanan exon junction and produce a 272 by fragment corresponding to murineTACI. Expression was detected in spleen, thymus, lung, breast, heart,muscle, skin, adrenal gland, stomach, small intestine, brain, ovary,prostate gland and embyro. Additional bands of ˜500 and 800 bp weredetected in many tissues.

Oligonucleotide primers ZC24198 (SEQ ID NO:29) and ZC24199 (SEQ IDNO:30) were designed to span an exon junction and produce a 204 byfragment corresponding to human TACI. Expression was detected in spleen,brain, heart, liver, colon, lung, small intestine, muscle, stomach,testis, placenta, salivary gland, adrenal gland, pancreas, prostate,peripheral blood lymphocytes and bone marrow.

Oligonucleotide primers ZC24271 (SEQ ID NO:31) and ZC24272 (SEQ IDNO:32) were designed to span an exon junction and produce a 329 byfragment corresponding to human BCMA. Expression was detected in brain,spleen, colon, lung, small intestine, stomach, ovary, testis, salivarygland, adrenal gland, prostate, peripheral blood lymphocytes, bonemarrow and fetal liver.

Oligonucleotide primers ZC24495 (SEQ ID NO:33) and ZC24496 (SEQ IDNO:34) were designed to span an exon junction and produce a 436 byfragment corresponding to murine BCMA. Expression was detected in liver.

Example 6 Preparation of TACI-Ig and BCMA-Ig Fusion Vectors

Ig Gamma1 Fc4 Fragment Construction

To prepare the TACI-Ig fusion protein, the Fc region of human IgG1 (thehinge region and the CH2 and CH3 domains) was modified so as to removeFc receptor (FcgRI) and complement (Clq) binding functions. Thismodified version of human IgG1 Fc was called Fc4.

The Fc region was isolated from a human fetal liver library (Clontech)by PCR using oligo primers ZC10,134 (SEQ ID NO:43) and ZC10,135 (SEQ IDNO:44). PCR was used to introduce mutations within the Fc region toreduce FcgRI binding. The FcgRI binding site (Leu-Leu-gly-Gly) wasmutated to Ala-Glu-gly-Ala (amino acid residues 38-41 of SEQ ID NO:45)according to Baum et al. (EMBO J. 13:3992-4001, 1994), to reduce FcR1binding (Duncan et al., Nature 332:563-4, 1988). Oligonucleotide primersZC15,345 (SEQ ID NO:46) and ZC15,347 (SEQ ID NO:47) were used tointroduce the mutation. To a 50 μl final volume was added 570 ng IgFctemplate, 5 μl 10×Pfu reaction Buffer (Stratagene), 8 μl of 1.25 mMdNTPs, 31 μl dH₂O, 2 μl 20 mM ZC15,345 (SEQ ID NO:46) and ZC15,347 (SEQID NO:47). An equal volume of mineral oil was added and the reaction washeated to 94° C. for 1 minute. Pfu polymerase (2.5 units, Stratagene)was added followed by 25 cycles at 94° C. for 30 seconds, 55° C. for 30seconds, 72° C. for 1 minute followed by a 7 minute extension at 72° C.The reaction products were electrophoresed and the band corresponding tothe predicted size of ˜676 by was detected. The band was excised fromthe gel and recovered using a QIAGEN QIAquick™ Gel Extraction Kit(Qiagen) according to the manufacturers instructions.

PCR was also used to introduce a mutation of Ala to Ser (amino acidresidue 134 of SEQ ID NO:45) and Pro to Ser (amino acid residue 135 ofSEQ ID NO:45) to reduce complement Clq binding and/or complementfixation (Duncan and Winter, Nature 332:788, 1988) and the stop codonTAA. Two, first round reactions were done using the FcγRI bindingside-mutated IgFc sequence as a template. To a 50 μl final volume wasadded 1 μl FcγRI binding site mutated IgFc template, 5 μl 10×RfuReaction Buffer (Stratagene), 8 μl 1.25 mM dNTPs, 31 μl dH₂O, 2 μl 20 mMZC15,517 (SEQ ID NO:48), a 5′ primer beginning at nucleotide 26 of SEQID NO:45 and 2 μl 20 mM ZC15,530 (SEQ ID NO:49), a 3′ primer beginningat the complement of nucleotide 405 of SEQ ID NO:45. The second reactioncontained 2 μl each of 20 mM stocks of oligonucleotide primers ZC15,518(SEQ ID NO:50), a 5′ primer beginning at nucleotide 388 of SEQ ID NO:45and ZC15,347 (SEQ ID NO:47), a 3′ primer, to introduce the Ala to Sermutation, Xba I restriction site and stop codon. An equal volume ofmineral oil was added and the reactions were heated to 94° C. for 1minute. Pfu polymerase (2.5 units, Stratagene) was added followed by 25cycles at 94° C. for 30 seconds, 55° C. for 30 seconds, 72° C. for 2minutes followed by a 7 minute extension at 72° C. The reaction productswere electrophoresed and bands corresponding to the predicted sizes,˜370 and ˜395 by respectively, were detected. The bands were excisedfrom the gel and extracted using a QIAGEN QIAquick™ Gel Extraction Kit(Qiagen) according to the manufacturers instructions. A second roundreaction was done to join the above fragments and add the 5′ Bam HIrestriction site. To a 50 μl final volume was added 30 μl dH2O, 8 μl1.25 mM dNTPs, 5 μl 10×Pfu polymerase reaction buffer (Stratagene) and 1μl each of the two first two PCR products. An equal volume of mineraloil was added and the reaction was heated to 94° C. for 1 minute. Pfupolymerase (2.5 units, Stratagene) was added followed by 5 cycles at 94°C. for 30 seconds, 55° C. for 30 seconds, and 72° C. for 2 minutes. Thetemperature was again brought to 94° C. and 2 μl each of 20 mM stocks ofZC15,516 (SEQ ID NO:51), a 5′ primer beginning at nucleotide 1 of SEQ IDNO:45, and ZC15,347 (SEQ ID NO:47) were added followed by 25 cycles at94° C. for 30 seconds, 55° C. for 30 seconds and 72° C. for 2 minutes,and a final 7 minute extension at 72° C. A portion of the reaction wasvisualized using gel electrophoresis. A 789 by band corresponding thepredicted size was detected.

TACI-Fc4 and BCMA-Fc4 Expression Vector Construction

Expression plasmids containing TACI-Fc4 and BCMA-Fc4 fusion proteinswere constructed via homologous recombination in yeast. A fragment ofTACI cDNA was isolated using PCR that included the polynucleotidesequence from nucleotide 15 to nucleotide 475 of SEQ ID NO:5. The twoprimers used in the production of the TACI fragment were: (1) a primercontaining 40 bps of the 5′ vector flanking sequence and 17 bpscorresponding to the amino terminus of the TACI fragment (SEQ ID NO:52);(2) 40 bps of the 3′ end corresponding to the flanking Fc4 sequence and17 by corresponding to the carboxyl terminus of the TACI fragment (SEQID NO:53). To an 100 μl final volume was added 10 ng TACI template, 10μl 10×Taq polymerase Reaction Buffer (Perkin Elmer), 8 μl 2.5 nM dNTPs,78 μl dH₂O, 2 μl each of 20 mM stocks of oligonucleotide primers SEQ IDNO:52 and SEQ ID NO:53, and taq polymerase (2.5 units, Life Technology).An equal volume of mineral oil was added and the reaction was heated to94° C. for 2 minutes, followed by 25 cycles at 94° C. for 30 seconds,65° C. for 30 seconds, 65° C. for 30 seconds, 72° C. for 1 minutefollowed by a 5 minute extension at 72° C.

A fragment of BCMA cDNA was isolated using PCR that includes thepolynucleotide sequence from nucleotide 219 to nucleotide 362 of SEQ IDNO:7. The two primers used in the production of the BCMA fragment werean oligonucleotide primer containing 40 bps of the 5′ vector flankingsequence and 17 bps corresponding to the amino terminus of the BCMAfragment (SEQ ID NO:54); and an oligonucleotide primer containing 40 bpsof the 3′ end corresponding to the flanking Fc4 sequence and 17 bpscorresponding to the carboxyl terminus of the BCMA fragment (SEQ IDNO:55). To a 100 μl final volume was added 10 ng BCMA template, 10 μl10×Taq polymerase Reaction Buffer (Perkin Elmer), 8 μl 2.5 mM dNTPs, 78μl H₂O, 2 μl each of 20 mM stock solutions of oligonucleotide primersSEQ ID NO:54 and SEQ ID NO:55. An equal volume of mineral oil was addedand the reaction was heated to 94° C. for 2 minutes, followed by 25cycles at 94° C. for 30 seconds, 65° C. for 30 seconds, 72° C. for 1minute followed by a 5 minute extension at 72° C.

The fragment containing the cDNA encoding the Fc4 fragment wasconstructed in a similar manner, one for each of the TACI and BCMAfusion constructs. For TACI the two primers used in the production ofthe Fc4 fragment were (upstream and downstream), an oligonucleotideprimer containing 40 bps of the 5′ TACI flanking sequence and 17 bpscorresponding to the amino terminus of the Fc4 fragment (SEQ ID NO:56);and an oligonucleotide primer containing 40 bps of the 3′ endcorresponding to the flanking vector sequence and 17 bps correspondingto the carboxyl terminus of the Fc4 fragment (SEQ ID NO:57). For BCMA,the upstream primer in the production of the Fc4 fragment was anoligonucleotide primer containing 40 bps of the 5′ BCMA flankingsequence and 17 bps corresponding to the amino terminus of the Fc4fragment (SEQ ID NO:58). The downstream primer for the Fc4 for the BCMAconstruct was the same as that described above for TACI-Fc4 (SEQ IDNO:57).

To a 100 μl final volume was added 10 ng Fc4 template described above,10 μl 10×Taq polymerase Reaction Buffer (Perkin Elmer), 8 μl 2.5 nMdNTPs, 78 μl dH₂O, 2 μl each of 20 mM stocks of oligonucleotides SEQ IDNO:56 and SEQ ID NO:57 for TACI and oligonucleotides SEQ ID NO:58 andSEQ ID NO:57 for BCMA, and taq polymerase (2.5 units, Life Technology).An equal volume of mineral oil was added and the reaction was heated to94° C. for 2 minutes, then 25 cycles at 94° C. for 30 seconds, 65° C.for seconds, 72° C. for 1 minute followed by a 5 minute extension at 72°C.

Ten microliters of each of the 100 μl PCR reactions described above wasrun on a 0.8% LMP agarose gel (Seaplaque GTG) with 1×TBE buffer foranalysis. The remaining 90 μl of each PCR reaction was precipitated withthe addition of 5 μl 1 M NaCl and 250 μl of absolute ethanol. Theplasmid pZMP6 was cut with SmaI to linearize it at the polylinker.Plasmid pZMP6 was derived from the plasmid pCZR199 (American TypeCulture Collection, Manassas, Va., ATCC#98668) and is a mammalianexpression vector containing an expression cassette having the CMVimmediate early promoter, a consensus intron from the variable region ofmouse immunoglobulin heavy chain locus, multiple restriction sites forinsertion of coding sequences, a stop codon and a human growth hormoneterminator. The plasmid also has an E. coli origin of replication, amammalian selectable marker expression unit having an SV40 promoter,enhancer and origin of replication, a DHFR gene and the SV40 terminator.The vector pZMP6 was constructed from pCZR199 by replacement of themetallothionein promoter with the CMV immediate early promoter, and theKozac sequences at the 5′ end of the open reading frame.

One hundred microliters of competent yeast cells (S. cerevisiae) werecombined with 10 μl containing approximately 1 μg each of either theTACI or the BCMA extracellular domain and the Fc4 PCR fragmentsappropriate for recombination with each, and 100 ng of SmaI digestedpZMP6 vector and transferred to a 0.2 cm electroporation cuvette. Theyeast/DNA mixtures were electropulsed at 0.75 kV (5 kV/cm), ∞ ohms, 25μF. To each cuvette was added 600 μl of 1.2 M sorbitol and the yeastwere plated in two 300 μl aliquots onto to URA-D plates and incubated at30° C.

After about 48 hours, the Ura+ yeast transformants from a single platewere resuspended in 1 ml H₂O and spun briefly to pellet the yeast cells.The cell pellet was resuspended in 1 ml of lysis buffer (2% TritonX-100, 1% SDS, 100 mM NaCl, 10 mM Tris, pH 8.0, 1 mM EDTA). Five hundredmicroliters of the lysis mixture was added to an Eppendorf tubecontaining 300 μl acid washed glass beads and 200 μl phenol-chloroform,vortexed for 1 minute intervals two or three times, followed by a 5minute spin in a Eppendorf centrifuge at maximum speed. Three hundredmicroliters of the aqueous phase was transferred to a fresh tube, andthe DNA precipitated with 600 μl ethanol (EtOH), followed bycentrifugation for 10 minutes at 4° C. The DNA pellet was resuspended in100 μl H₂O.

Transformation of electrocompetent E. coli cells (DH10B, GibcoBRL) wasdone with 0.5-2 ml yeast DNA prep and 40 μl of DH10B cells. The cellswere electropulsed at 2.0 kV, 25 mF and 400 ohms. Followingelectroporation, 1 ml SOC (2% Bacto′ Tryptone (Difco, Detroit, Mich.),0.5% yeast extract (Difco), 10 mM NaCl, 2.5 mM KCl, 10 mM MgCl2, 10 mMMgSO4, 20 mM glucose) was plated in 250 μl aliquots on four LB AMPplates (LB broth (Lennox), 1.8% Bacto′ Agar (Difco), 100 mg/LAmpicillin).

Individual clones harboring the correct expression construct forTACI-Fc4 or BCMA-Fc4 were identified by restriction digest to verify thepresence of the insert and to confirm that the various DNA sequenceshave been joined correctly to one another. The insert of positive cloneswere subjected to sequence analysis. Larger scale plasmid DNA isisolated using the Qiagen Maxi kit (Qiagen) according to manufacturer'sinstruction

Example 7 Mammalian Expression of TACI-Fc4 and BCMA-Fc4

BHK 570 cells (ATCC NO: CRL-10314) were plated in 10 cm tissue culturedishes and allowed to grow to approximately 50 to 70% confluencyovernight at 37° C., 5% CO2, in DMEM/FBS media (DMEM, Gibco/BRL HighGlucose, (Gibco BRL, Gaithersburg, Md.), 5% fetal bovine serum (Hyclone,Logan, Utah), 1 mM L-glutamine (JRH Biosciences, Lenexa, Kans.), 1 mMsodium pyruvate (Gibco BRL)). The cells were then transfected witheither the plasmid TACI-Fc4/pZMP6 or BCMA-Fc4/pZMP6, usingLipofectamine™ (Gibco BRL), in serum free (SF) media formulation (DMEM,10 mg/ml transferrin, 5 mg/ml insulin, 2 mg/ml fetuin, 1% L-glutamineand 1% sodium pyruvate). TACI-Fc4/pZMP6 or BCMA-Fc4/pZMP6 was dilutedinto 15 ml tubes to a total final volume of 640 μl with SF media. 35 μlof Lipofectamine™ (Gibco BRL) was mixed with 605 μl of SF medium. TheLipofectamine™ mix was added to the DNA mix and allowed to incubateapproximately 30 minutes at room temperature. Five milliliters of SFmedia was added to the DNA:Lipofectamine™ mixture. The cells were rinsedonce with 5 ml of SF media, aspirated, and the DNA:Lipofectamine™mixture is added. The cells were incubated at 37° C. for five hours,then 6.4 ml of DMEM/10% FBS, 1% PSN media was added to each plate. Theplates were incubated at 37° C. overnight and the DNA:Lipofectamine™mixture was replaced with fresh 5% FBS/DMEM media the next day. On day 5post-transfection, the cells were split into T-162 flask in selectionmedium (DMEM/5% FBS, 1% L-GLU, 1% NaPyr). Approximately 10 dayspost-transfection, two 150 mm culture dishes of methotrexate resistantcolonies from each transfection were trypsinized and the cells arepooled and plated into a T-162 flask and transferred to large scaleculture.

Example 9 Transgenic Expression of Ztnf4

Transgenic animals expressing ztnf4 genes were made using adult, fertilemales (B6C3f1), prepubescent fertile females (B6C3f1), vasectomizedmales (B6D2f1), and adult fertile females (B6D2f1) (all from TaconicFarms, Germantown, N.Y.). The prepubescent fertile females weresuperovulated using Pregnant Mare's Serum gonadotrophin (Sigma, St.Louis, Mo.) and human Chorionic Gonadotropin (hCG (Sigma)). Thesuperovulated females were subsequently mated with adult, fertile males,and copulation was confirmed by the presence of vaginal plugs.

Fertilized eggs were collected under a surgical scope (Leica MZ12 StereoMicroscope, Leica, Wetzlar, Germany). The eggs were then washed inhyaluronidase and Whitten's W640 medium (Table 8; all reagents availablefrom Sigma Chemical Co.) that has been incubated with 5% CO2, 5% O₂, and90% N₂ at 37° C. The eggs were stored in a 37° C./5% CO₂ incubator untilmicroinjection.

TABLE 8 WHITTEN'S 640 MEDIA mgs/200 ml mgs/500 ml NaCl 1280 3200 KCl  72 180 KH₂PO₄  32  80 MgSO₄-7H₂O  60  150 Glucose  200  500 Ca²⁺ Lactate 106  265 Benzylpenicillin  15  37.5 Streptomycin SO₄  10  25 NaHCO₃ 380  950 Na Pyruvate   5  12.5 H₂0  200 ml  500 ml 500 mM EDTA  100 μl 250 μl 5% Phenol Red  200 μl  500 μl BSA  600 1500

The 858 by open reading frame encoding full length human TACI ligandBlys (SEQ ID NO:35) was amplified by PCR so as to introduce an optimizedinitiation codon and flanking 5′ PmeI and 3′ AscI sites using theoligonucleotide primers of SEQ ID NO:36 and SEQ ID NO:37. This PmeI/AscIfragment was subcloned into pKF024, a B and/or T cell-restrictedtransgenic vector containing the Ig Em enhancer (690 bp NotI/XbaI frompEmSR; (Bodrug et al., EMBO J. 13:2124-30, 1994), the Ig V_(h) promoter(536 by HincII/XhoI fragment from pJH1X(−); Hu et al., J. Exp. Med.177:1681-90, 1993), the SV40 16S intron (171 by XhoI/HindIII fragmentfrom pEmSR), a PmeI/AscI polylinker, and the human growth hormone genepolyadenylation signal (627 by SmaI/EcoRI fragment; Seeburg, DNA1:239-49, 1982). The transgene insert was separated from plasmidbackbone by NotI digestion and agarose gel purification, and fertilizedova from matings of B6C3F1Tac mice described above were microinjectedand implanted into pseudopregnant females essentially as previouslydescribed (Malik et al., Molec. Cell. Biol. 15:2349-58, 1995)

The recipients were returned to cages in pairs, and allowed 19-21 daysgestation. After birth, 19-21 days postpartum was allowed before sexingand weaning, and a 0.5 cm biopsy (used for genotyping) was snipped offthe tail with clean scissors.

Genomic DNA was prepared from the tail snips using a commerciallyavailable kit (DNeasy 96 Tissue Kit; Qiagen, Valencia, Calif.) followingthe manufacturer's instructions. Genomic DNA was analyzed by PCR usingprimers designed to the human growth hormone (hGH) 3′ UTR portion of thetransgenic vector. Primers ZC17251 (SEQ ID NO:38) and ZC17252 (SEQ IDNO:39) amplify a 368-base-pair fragment of hGH. The use of a regionunique to the human sequence (identified from an alignment of the humanand mouse growth hormone 3′ UTR DNA sequences) ensured that the PCRreaction did not amplify the mouse sequence. In addition, primersZC17156 (SEQ ID NO:40) and ZC17157 (SEQ ID NO:41), which hybridize tovector sequences and amplify the cDNA insert, may be used along with thehGH primers. In these experiments, DNA from animals positive for thetransgene generated two bands, a 368-base-pair band corresponding to thehGH 3′ UTR fragment and a band of variable size corresponding to thecDNA insert.

Once animals were confirmed to be transgenic (TG), they are back-crossedinto an inbred strain by placing a TG female with a wild-type male, or aTG male with one or two wild-type female(s). As pups were born andweaned, the sexes were separated, and their tails snipped forgenotyping.

To check for expression of a transgene in a live animal, a survivalbiopsy is performed. Analysis of the mRNA expression level of eachtransgene was done using an RNA solution hybridization assay orreal-time PCR on an ABI Prism 7700 (PE Applied Biosystems, Inc., FosterCity, Calif.) following the manufacturer's instructions.

Cell Preparation and Flow Cytometry

Founder mice were analyzed at various ages. For flow cytometric (FACS)analysis of lymphoid tissues, bone marrow (BM) cells were isolated fromfemurs and tibias by careful disruption in phosphate-buffered saline(PBS) using a mortar and pestle. Cells were resuspended, depleted ofbone fragments by passive sedimentation, and pelleted at 1000×g.Splenocytes, thymocytes, or lymph node cells were obtained by crushingintact tissues between glass slides, then resuspending and pelleting thecells as for BM. Cells were resuspended in FACS wash buffer (FACS WB)(Hank's balanced salt solution, 1% BSA, 10 mM Hepes, pH 7.4) at aconcentration of 20×10⁶ cells/ml prior to staining. To stain, 1×10⁶cells were transferred to 5 ml tubes and washed with 1 ml of FACS WB,then pelleted at 1000×g. Cells were then incubated on ice for 20 minutesin the presence of saturating amounts of the appropriate FITC-, PE-and/or TriColor (TC)-conjugated mAbs in a total volume of 100 ml in FACSWB. Cells were washed with 1.5 ml of WB, pelleted, then resuspended in400 ml WB and analyzed on a FACSCalibur flow cytometer using CellQuestsoftware (Becton Dickinson, Mountain View, Calif.). Detectors forforward (FSC) and side (SSC) light scatter were set on a linear scale,whereas logarithmic detectors were used for all three fluorescencechannels (FL-1, FL-2, and FL-3).

Compensation for spectral overlap between FL channels was performed foreach experiment using single color stained cell populations. All cellswere collected ungated to disk and data were analyzed using CellQuestsoftware. RBC and dead cells were excluded by electronically gating dataon the basis of FSC vs. SSC profiles.

Antibodies

Fluorescein isothiocyanate (FITC)-conjugated anti-CD8 monoclonalantibody (mAb) (clone 53-6.7) and phycoerthyrin (PE)-conjugated anti-CD4(cloneRM4-5), anti-CD5 (clone 53-7.3), anti-CD19 (clone 1D3), andanti-syndecan (clone 281-2) mAbs were purchased from PharMingen (SanDiego, Calif.). TriColor (TC)-conjugated anti-CD45R/B220 mAb (cloneRA3-6B2) was purchased from Caltag.

Transgenic mice over expressing ztnf4 in the lymphoid compartmentdevelop increased numbers of peripheral B cells, increased plasma cellsand elevated levels of serum immunoglobulin. These transgenic animalshave an increased number of B200+ cells in the spleen, lymph nodes andthymus. The increased number of splenic B cells includes bothconventional B-2 cells, and the normally rare population of B-1 cells.In general, B-1 cells are largely confined to the peritoneal and otherbody cavities, produce low affinity self-reactive antibodies, and haveoften been associated with the development of autoimmune diseases suchas systemic lupus erythematosus SLE.

Older transgenic animals produce autoantibodies, develop proteinurea andsclerotic glomeruli, characteristics of systemic lupus erythematosus.

FIG. 5A shows single cell suspensions of spleen (top panel), mesentericlymph node (middle panel), and bone marrow (lower panel) prepared asdescribed below, stained with anti-B220-TC and analyzed by flowcytometry. The number of B220+ cells in each tissue was calculated bymultiplying the percent B220+ cells by the total number of live (trypanblue excluding) cells counted on a hemocytometer. Each bar representsdata from individual ztnf4 transgenic (Tg, shaded bars) or nonTGlittermate (open bars) control mice.

FIG. 5B shows cells isolated from ztnf4 TG (right-hand panels) or nonTGlittermate (left-hand panels) lymph node (top row), spleen (middlerows), and thymus (bottom row) were stained with mAbs to the moleculesindicated (DC5, CD4 and CD8), then analyzed by flow cytometry. Datashown were gated to exclude dead cells and RBCs.

FIG. 5C shows total IgG, IgM, and IgE levels in serum from ztnf4transgenic mice ranging in age from 6 to 23 weeks old.

Histology revealed amyloid deposition and thickened mesangium of theglomeruli identified in H&E stained kidney sections from ztnf4transgenic mice compared to normal glomeruli from control littermates.

FIG. 5D shows an increase in effector T cells in ztnf4 transgenic mice,similar to that reported by Mackay et al. (J. Exp. Med. 190:1697-1710,1999).

Soluble TACI(BR43x2) or BCMA-Ig fusions are injected (IP, IM or IV) intoztnf4 over expressing transgenic animals. Flow cytometric (FACS)analysis of lymphoid tissues will be used to identify any change in thenumber of B220+ B cells in the spleen, lymph nodes and thymus.

Example 10 Direct Binding ELISA

A direct binding ELISA was developed to characterize the ability ofeither soluble TACI-Ig or soluble BCMA-Ig to bind and inhibit thebiological activity of ztnf4 in vitro.

A 96 well plate was coated with 1 μg/ml Goat-anti-Human Ig (JacksonLabs, Bar Harbor, Mass.) in ELISA A buffer (0.1 M Na₂HCO₃, pH 9.6, 0.02%NaN₃) and incubated overnight at 4° C. TACI, BCMA, and an unrelated TNFreceptor such as ztnfr10 (SEQ ID NO:42) as a control were titered from10 μg/ml through 5 fold dilutions to 320 ng/ml plus a zero andco-incubated with 2.5, 0.5, or 0.1 μg/ml biotinylated ztnf4 or ovalbuminas a negative control, and incubated 1 hour at room temperature.

The co-incubated receptor-biotinylated ligand mixture was then added tothe goat-anti-human Ig coated 96 well plates. The plates were thenwashed (ELISA C, 500 μl Tween 20 (Sigma Chemical Co., St. Louis, Mo.),200 mg NaN₃, PBS to a final volume of 1 liter) and blocked withSuperblock (Pierce, Rockford, Ill.). The plates were then incubated at37° C. for 2 hours.

The plates are once again washed with ELISA C followed by the additionof 100 μl/well of neutr-avidin-HRP at 1:10,000 in ELISA B (5 or 10 μgBSA (Sigma) for 1% or 2% BSA, respectively, 250 μl Tween 20 (Sigma), 100mg NaN₃, phosphate-buffered saline pH 7.2 (PBS, Sigma) to a final volumeof 500 ml. Alternatively, the buffer may be made up as 1% or 2% BSA inELISA C Buffer). The plates are then developed with OPD for 10 minutesat room temperature and read at 492.

Example 11 Biological Activity Assay

A biological activity assay was developed to measure soluble TACI-FCinhibition of human B cell the stimulation by soluble ztnf4. B cellswere isolated from peripheral blood mononuclear cells (PBMNC) using CD19magnetic beads and the VarioMacs magnetic separation system (MiltenyiBiotec Auburn, Calif.) according to the manufacturer's instructions.Purified B cells were mixed with soluble ztnf4 (25 ng/ml) andrecombinant human IL-4 (10 ng/ml Pharmingen) and were plated (intriplicate) on to round bottom 96 well plates at 1×10⁵ cells per well.

Soluble TACI-FC was diluted from 5 μg/ml to 6 ng/ml and incubated withthe B cell for 5 days, pulsing overnight on day 4 with 1 μCi ³HThymidine (Amersham) per well. As a control soluble TACI-FC was alsoincubated with B cells and IL-4 without ztnf4 present.

Plates were harvested using Packard plate harvester and counted usingthe Packard reader. The TACI-Ig soluble receptor inhibited the abilityof soluble ztnf4 to stimulate B cell proliferation in vitro in adose-dependent manner. A 10-fold molar excess TACI-Ig completelyinhibits the proliferation of human B cells in response to soluble ztnf4in the presence of IL-4.

Example 12 ORIGIN Assay

Levels of ztnf4 in individuals with a disease condition (such as SLE,rheumatoid arthritis for example) relative to normal individuals weredetermined using an electrochemiluminescence assay. A standard curveprepared from soluble, human ztnf4 at 10 ng/ml, 1 ng/ml, 0.1 ng/ml, 0.01ng/ml and 0 ng/ml was prepared in ORIGIN buffer (Igen, Gaithersburg,Md.). Serum samples were diluted in ORIGIN buffer. The standards andsamples were incubated at room temperature for 2 hours with biotinylatedrabbit anti-human ztnf4-NF BV antibody diluted to 1 μg/ml in OriginAssay Buffer (IGEN) and ruthenylated rabbit anti-human ztnf4-NF BVpolyclonal antibody diluted to 1 μg/ml in Origin Assay Buffer (IGEN).Following the incubation the samples were vortexed and 0.4 mg/mlstreptavidin Dynabeads (Dynal, Oslo, Norway) were added to each of thestandards and samples at 50 μl/tube and incubated for 30 minutes at roomtemperature. Samples were then vortexed and samples were read on anOrigin Analyzer (Igen) according to manufacturer's instructions. TheOrigin assay is based on electrochemiluminescence and produces a readoutin ECL.

An elevated level of ztnf4 was detected in the serum samples from bothNZBWF1/J, and MRL/Mpj-Fas^(lpr) mice which have progressed to advancedstages of glomerulonephritis and autoimmune disease.

Example 13 Soluble TACI-Ig in a Spontaneous Model of SLE

NZBW mice become symptomatic for spontaneous SLE at approximately 7-9months of age. TACI-Fc was administered to NZBW mice to monitor itssuppressive effect on B cells over the 5 week period when, on average,B-cell autoantibody production is thought to be at high levels in NZBWmice.

One hundred, 8-week old female (NZB×NZW)F₁ mice (Jackson Labs) weredivided into 6 groups of 15 mice. Prior to treatment the mice weremonitored once a month for urine protein and blood was drawn for CBC andserum banking. Serum will be screened for the presence ofautoantibodies. Because proteinuria is the hallmark sign ofglomerulonephritis, urine protein levels were monitored by dipstick atregular intervals over the course of the study. Prior to treatment theanimals were weighed. Dosing was started when mice were approximately 5months of age. The mice received intraperitoneal injections of vehicleonly (PBS) or human IgG-FC (control protein) or TACI-FC4 (test protein)three times a week for 5 weeks, Table 9.

TABLE 9 Group (5 mice each) Treatment Dose 1 untreated control 2 vehicleonly 3 human IgG-FC  20 μg 4 human IgG-FC 100 μg 5 human TACI-FC4  20 μg6 human TACI-FC4 100 μg

Blood was collected twice during dosing and will be collected at leasttwice following dosing. Urine dipstick values for proteinuria and bodyweights were made every two weeks after dosing begins. Blood, urinedipstick value and body weight were collected at the time of euthanasia.Weight of spleen, thymus, liver with gall bladder, left kidney and brainwere taken. The spleen and thymus were divided for FACS analysis andhistology. Submandibular salivary glands, mesenteric lymph node chain,liver lobe with gall bladder, cecum and large intestine, stomach, smallintestine, pancreas, right kidney, adrenal gland, tongue with tracheaand esophagus, heart and lungs will also be collected for histology.

FIG. 6 shows an elevated level of ztnf4 in serum from NZBWF1 andMRL/lpr/lpr mice that correlates with the development of SLE. FIG. 6Aupper panel shows the correlation of ztnf4 serum levels with age, 68NZBWF1 mice ranging from 10 to 40 weeks old and 10 week and 30 week oldNZB/B control mice. The middle panel shows the correlation withproteinuria at three ranges, trace to 20 mg/dl (T-30), 100-300 ng/dl and2000 mg/dl in NZBWF1 mice compared to control NZB/B mice. The lowerpanel shows ztnf4 levels with various titers of anti-ds DNA antibody inNZBWF1 mice compared to control NZB/B mice:

FIG. 6B shows the same correlations made on 23 MRL/lpr/lpr mice rangingfrom 18-24 weeks old and 10 control 11 week old MRL/MpJ mice.

FIG. 7 shows urinalysis results. Mice were considered to haveproteinuria if the dipstick reading was ≧100 mg/dl. (A) PBS, (B) humanIgG FC, 100 mg, (C) human IgG FC, 20 mg, (D) human TACI-IgG, 100 mg, and(E) human TACI-IgG, 20 mg. Mice treated with the soluble TACI-IgG fusionshowed a reduction in proteinuria.

Analysis of peripheral blood from treated animals revealed that whiteblood cell and lymphocyte counts were reduced in TACI-FC treated mice(20 and 100 mg) when compared to FC (20 and 100 mg) and PBS treatedmice, 2 weeks after the start of treatment. FAC analysis (lymphocytegate) of peripheral blood drawn six weeks after treatment began (twoweeks after last treatment was administered) and showed a dramaticdecrease in percentage of B cells present in the samples. B cell levelswere still in decline at five weeks after last treatment wasadministered, but not as dramatic. Table 9 provides the average (andstandard deviation) for the mice in each treatment group (Table 10). Thedecline in the percent of B cells in peripheral blood was also observedtwo weeks into treatment.

TABLE 10 Week 2 Week 5 Treatment % B cells % T cells % B cells PBS 26.05(6.52) 67.05 (6.80) 20.83 (3.14) 100 mg FC 23.34 (5.77) 68.23 (7.30)25.04 (8.07)  20 mg FC 24.09 (6.26) 65.27 (7.18) 18.96 (6.42) 100 mgTACI-FC 11.07 (5.03) 79.06 (6.71) 14.79 (4.76)  20 mg TACI-FC 16.37(7.27) 69.72 (8.90) 19.14 (5.27)

Example 14 Soluble TACI-Ig in Normal Mice

TACI-FC was administered to Blab/C mice to monitor its effect on normalmice. Sixty, 8-week old female Balb/C mice (HSD) were divided into 12groups of 5 mice. Prior to treatment the mice were weighed and blood wasdrawn for CBC and serum banking. Groups 1-9 received intraperitonealinjections (IP) of vehicle only (PBS) or human IgG-FC (control protein)or TACI-FC4 (test protein) daily for 12 days and were sacrificed on day14. Groups 10 and 11 received IP injections three times per week for twoweeks and were sacrificed on day 14, Table 11.

TABLE 11 Group (5 mice each) Treatment Dose 1 human TACI-FC4 200 mg 2human TACI-FC4 100 mg 3 human TACI-FC4 20 μg 4 human TACI-FC4 5 μg 5human FC4 200 μg 6 human FC4 100 mg 7 human FC4 20 mg 8 human FC4 5 mg 9vehicle only as used 10 human TACI-FC4 100 mg 11 human FC4 100 mg 12untreated control

Blood was collected on days 7 and 12. Blood and body weight werecollected at the time of euthanasia. Weight of spleen, thymus, and brainwere taken. The spleen and thymus were divided for FACS analysis andhistology. Skin, spleen, mesenteric LN chain, submandibular salivaryglands, ovary, uterus, cervix, bladder, mesenteric lymph node chain,liver lobe with gall bladder, cecum and large intestine, stomach, smallintestine, pancreas, right kidney, adrenal gland, tongue with tracheaand esophagus, heart, thymus, thigh muscle, left and right femur, brainwill also be collected for histology.

As described above in Example 13, a significant reduction in percent Bcells was seen on days 7 (by CBC) and 12 (using FACS) in peripheralblood cells taken from all TACI-FC4 treated samples compared to thosetreated with FC4 or PBS alone and analyzed by CBC or FACS. Additionally,there was nearly a 50% decrease in B cells in the spleens taken fromanimals treated with TACI-FC4 as compared to those from FC4 treated miceday 14.

The mice tolerated TACI-FC4 and exhibited no overt health problems. Atnecropsy, no detectable adverse pathological effect of the TACI-FC4treatment was observed in the histology performed on the collectedorgans and tissues. Thymus, spleens, and bone marrow from the animals ineach group were pooled and analyzed by flow immunocytometry for T, B andmonocyte cell populations in the spleen, T cell subsets in the thymusand immature and mature B cell populations in the bone marrow. There wasa 60% drop in the ratio of B to T cells in the spleens of TACI-FC4treated mice compared with control protein and PBS at the time ofsacrifice. This inhibition was detected at 200, 100, and 20 μg dailydoses and at the 100 μg dose given three times a week (Table 11a). Therewere no observable changes in other cell populations in the lymphoidorgans analyzed, Table 12a.

To further define the effect of TACI-FC4 on lymphoid cell populations inbone marrow, thymus, spleen, mesenteric lymph nodes and peritonealexudates cells a second group of mice were treated with 100 μg TACI-FC,FC4, or PBS, three times a week for two weeks.

There were no changes in T cell number or CD4 or CD8 T cell subsets inthe thymus or lymph node and no changes in the number of CD11b⁺monocytes in the spleen. Mature B cell populations were characterizedusing antibodies to the cell surface markers CD21, CD23, and B220 in thespleen and IgM, IgD and B220 in the spleen, lymph noted and bone marrow.TACI-FC4 has an effect on the mature B cell populations in spleen, lymphnode and bone marrow, and does not appear to have an effect on immatureB220+ bone marrow B cells, mature T cells, or monocytes (Table 12b). Anincrease in the newly formed B cell population in the spleen and lymphnode was also detected.

Serum IgM and IgG were in each mouse two days prior to sacrifice. IgMlevels decreased while IgG levels remained the same.

TABLE 12a Lymphocyte Populations Spleen (×10⁷) B T Monocyte PBS 6.8 6.90.5 FC4 6.9 5.1 0.4 TACI-FC4 4.1 5.5 0.4

TABLE 12b B220+ B-cell Population Spleen (×10⁶) Newly Formed FollicularB Marginal Zone CD23^(lo)CD21^(lo) CD23^(hi)CD21^(hi) CD23^(lo)CD21^(hi)PBS  5.1 53.0 8.8 FC4  5.4 54.3 7.7 TACI-FC4 14.8 17.0 6.0 B220+ b-CellPopulations in the Bone Marrow (×10⁶) Pre-Pro B Immature B MatureB220^(mid)IgM⁻IgD⁻ B220^(mid)IgM⁺IgD⁻ B220^(hi)IgM⁺IgD⁺ PBS 38.0 37.09.34 FC4 38.3 38.8 9.46 TACI-FC4 47.9 47.9 5.6 

Example 15 Anti-dsDNA ELISA

Autoimmunity is characterized by high levels of anti-double stranded DNAantibodies. To measure the levels anti-dsDNA antibodies in both the overexpressing ztnf4 transgenic mice and the NZBW mice an ELISA assay wasdeveloped. A 96 well microtiter plate (Nunc) was coated withpoly-L-lysine (Sigma) (20 μl/ml in 0.1 M Tris buffer pH 7.3) at 75μl/well and incubated overnight at room temperature. The plates werethen washed in dH₂O and coated with poly dAdT (Sigma) (20 μl/ml in 0.1 MTris buffer pH 7.3) at 75 μl/well and incubated at room temperature for60 minutes. The plates were then washed with dH₂O and blocked with 2%BSA (Sigma) in Tris Buffer for 30 minutes at room temperature followedby a final wash in dH₂O.

Serum samples were taken from the ztnf4 transgenic mice described inExample 10 and the NZBW mice described in Example 11. The serum sampleswere diluted 1:50 in 1% BSA/2% BGG (Calbiochem) in Tris Buffer. Thediluted samples were then titrated into the coated plate at 1:50, 1:100,1:200, 1:400, 1:800, 1:1600, 1:3200 and 1:6400 (50 μl/well) andincubated for 90 minutes at room temperature.

Plates were then washed in dH₂O and goat anti-mouse IgG-Fc-HRP (Cappel)diluted to 1:1000 in 1% BSA/2% BGG was added at 50 μl/well. The plateswere incubated for 60 minutes at room temperature. The plates werewashed 5× in dH₂O and developed with OPD, 1 tablet/10 ml Novo D (313 ml0.1M Na Citrate, 187 ml 0.1M citric acid, pH 5.0) and plated at 100μl/well. The developer was stopped with 1N H₂SO₄, 100 μl/well, and theOD read at 492 nm.

FIG. 8 shows the anti-ds DNA levels in two ztnf4 transgenic mice (23week old), two non-transgenic litter mates compared with the levelsdetected in serum from NZBWF1 (32 week old) and MRL/lpr/lpr (19 weekold) mice.

Example 16 Soluble TACI-Ig in a Spontaneous Model of EAE

Twenty five female PLxSJL F1 mice (12 weeks old, Jackson Labs) are givena subcutaneous injection of 125 μg/mouse of antigen (myelin ProteolipidProtein, PLP, residues 139-151), formulated in complete Freund'sAdjuvant. The mice are divided into 5 groups of 5 mice. Intraperitonealinjections of pertussis toxin (400 ng) are given on Day 0 and 2. Thegroups will be given a 1×, 10×, or 100× dose of TACI, BCMA or BR43x2,one group will receive vehicle only and one group will receive notreatment. Prevention therapy will begin on Day 0, intervention therapywill begin on day 7, or at onset of clinical signs. Signs of disease,weight loss, and paralysis manifest in approximately 10-14 days, andlast for about 1 week. Animals are assessed daily by collecting bodyweights and assigning a clinical score to correspond to the extent oftheir symptoms. Clinical signs of EAE appear within 10-14 days ofinoculation and persist for approximately 1 week. At the end of thestudy all animals are euthanized by gas overdose, and necropsied. Thebrain and spinal column are collected for histology or frozen for mRNAanalysis. Body weight and clinical score data is plotted by individualand by group.

Clinical Score 0 Normal 0.5 Weak, tail tone may be reduced but notabsent 1 Limp tail (cannot lift tail when mouse is picked up at base oftail) 2 Limp tail, weak legs (cannot lift tail, can stay upright on hindlegs but legs are shaky) 3 Paresis (cannot sit with legs under body,walk in a paddling motion with legs behind) 4 Paralysis (cannot moveback legs, drags legs when trying to walk) 5 Quadriplegia (paralysis infront legs or walking in a circular pattern, may have head tilt) 6Moribund (completely paralyzed, cannot reach food or water, sacrificeanimal)

Example 17 TACI-FC and the CIA Model for Rheumatoid Arthritis

Male DBA/1J mice (Jackson Labs), eight to twelve weeks old, were dividedinto groups, 5 mice/group, and given two subcutaneous injections of50-100 μl of 1 mg/ml collagen (chick), 3 weeks apart. One control didnot receive collagen injections. The first injection was formulated inComplete Freund's Adjuvant and the second injection was formulated inIncomplete Freund's Adjuvant. TACI-Fc, a control protein, human IgFc, orPBS (vehicle) was administered prophylactically beginning 7 days priorto the second injection (day −7). All dosing was done at 100 μg, given 3times a week as a 200 μl intraperitoneal (IP) injection and werecontinued for 4 weeks.

The animals develop antibodies to the foreign collagen, and in thismouse strain, cross-reactivity to their own native joint cartilage isknown to occur. The antibody deposition produces localized jointinflammation and joint destruction very similar to human rheumatoidarthritis. The disease occurrence and severity have been closelycorrelated with anti-collagen antibody titer levels. Symptoms usuallyappear within 2-3 weeks of the second injection, but may range from 1-6weeks.

Extent of disease was evaluated in each paw by using a caliper tomeasure paw thickness and assigning a clinical score (0-3) to each paw.

Clinical Score 0 Normal 1 Toe(s) inflamed 2 Mild paw inflammation 3Moderate paw inflammation 4 Severe paw inflammation

In this study, an animal was said to have “established disease” once apaw maintains a score of 2 or more for one day. Animals were euthanizedafter having established disease for a set period of time, usually 7days. Study events were typically defined relative to Day 0, which wasdefined as the day of the second collagen collection. Paws werecollected for histology or mRNA analysis, and serum was collected forimmunoglobulin and cytokine assays.

When TACI-Fc was administered prophylactically, there was a marked onsetof disease. While the control protein or vehicle groups averaged 50%disease incidence by day 6, the TACI-Fc group averaged 50% incidence byday 15. There was a pronounced reduction in disease severity as shown byboth a lower incidence of established disease in the TACI-Fc treatedgroups as compared to all controls, and a longer time for establisheddisease to occur in the TACI-Fc group.

A second prophylactic study corroborated these results. As describedabove, TACI-Fc, control protein human Ig-Fc or PBS (vehicle) wereadministered as a therapeutic, beginning 7 days following the secondcollagen injection (day +7). All dosing was again at 100 μg given 3times a week as a 200 μl IP injection, and was continued for 4 weeks.Animals in all groups developed disease at the same rate, but diseaseseverity was greatly reduced in the TACI-Fc-treated animals. This wasevidenced by a marked reduction in their incidence of “establisheddisease” as described above. By day 38 the therapeutically treatedTACI-Fc group had an incidence rate of just 58% for established disease,as compared to 95% or 100% for the control groups (control protein andvehicle, respectively). The therapeutically treated TACI-Fc group alsocompares well to the prophylactically-treated TACI-Fc groups asdescribed above, which had a slightly better incidence rate of 50%. Thisis especially noteworthy given that the therapeutically treated TACI-Fcgroups already had a 10% incidence of established disease prior toinitiating dosing on day 7.

Serum samples were collected from prophylactically treated andtherapeutically treated mice on day −3, day 14 after second collageninjection and day (from therapeutically treated mice only) to determinecollagen levels by ELISA.

One hundred μl collagen (Chondrex Redmond, Wash.) was diluted in 10 mldiluent (1 ml 10× buffer (Chondrex), ml water) and microtiter plates(Nunc AS, Roskilde, Denmark) were coated with collagen at 100 μl/welland incubated overnight at 4° C., then washed with ELISA C buffer. Theplates were then blocked (200 μl/well) with SuperBlock (Pierce,Rockford, Ill.) at room temperature for 5 minutes, then washed withELISA C.

Samples were diluted in ELISA B (1% bovine serum albumin, ELISA C),making serial 5 fold dilutions from 1:5000 to 1:625,000 and plated intriplicate at 100 μl/well. The plates were incubated overnight at 4° C.or for 2 hours at room temperature, followed by washing with ELISA C.

Goat anti-mouse Ig-HRP (Zymed, South San

Francisco, Calif.) was diluted 1:2000 in ELISA B and plated at 100μl/well. The plates were incubated at room temperature for 90 minutesthen washed with ELISA C.

The plates were developed by plating OPD (1 OPD tablet (Sigma ChemicalCo., St. Louis, Mo.), 10 ml Novo D, 10 μl H₂O₂) at 100 μl/well.Development was stopped with 1N H₂SO₄ at 100 μl/well and the plates wereread at an OD of 490 nm.

FIG. 9A shows that in TACI-Fc treated mice the level of anti-collagenantibodies is reduced 5-7 days after treatment when compared to controlmice, and the level of anti-collagen antibodies continues to decreasewith further TACI-Fc treatments.

FIG. 9B shows a drop in collagen antibodies 5 days after the initialcollagen treatment in all mice treated. Following the second collagentreatment those mice treated with TACI-Fc show a continued decrease inanti-collagen antibodies until sacrifice, while the levels ofanti-collagen antibodies in control mice increase with time.

Example 18 Neutralizing TACI Antibodies

Polyclonal anti-peptide antibodies were prepared by immunizing 2 femaleNew Zealand white rabbits with the peptide, hurtnf4-1SAGIAKLEEGPELQLAIPRE (SEQ ID NO:59) or hurtnf4-2 SFKRGSALEEKENKELVKET(SEQ ID NO:60). The peptides were synthesized using an AppliedBiosystems Model 431A peptide synthesizer (Applied Biosystems, Inc.,Foster City, Calif.) according to manufacturer's instructions. Thepeptides were then conjugated to the carrier protein keyhole limpethemocyanin (KLH) with maleimide-activation. The rabbits were each givenan initial intraperitoneal (ip) injection of 200 μg of peptide inComplete Freund's Adjuvant followed by booster ip injections of 100 μgpeptide in Incomplete Freund's Adjuvant every three weeks. Seven to tendays after the administration of the second booster injection (3 totalinjections), the animals were bled and the serum was collected. Theanimals were then boosted and bled every three weeks.

The ztnf4 peptide-specific rabbit seras were characterized by an ELISAtiter check using 1 μg/ml of the peptides used to make the antibody (SEQID NOs:59 and 60) as an antibody target. The 2 rabbit seras to thehurtnf4-peptide (SEQ ID NO:59) have titer to their specific peptide at adilution of 1:1 E5 (1:100000). The 2 rabbit seras to the hurtnf4-2peptide (SEQ ID NO:60) had titer to their specific peptide at a dilutionof 1:5 E6 and to recombinant full-length proteins (N-terminalFLAG-tagged ztnf4 made in baculovirus (hurtnf4s-NF-Bv) and C-terminallyFLAG-tagged ztnf4 made in BHK cells) at a dilution of 1:5 E6.

The ztnf4 peptide-specific polyclonal antibodies were affinity purifiedfrom the rabbit serum using CNBR-SEPHAROSE 4B protein columns (PharmaciaLKB) that were prepared using 10 mgs of the specific peptides (SEQ. ID.NOs. 59 or 60) per gram CNBr-SEPHAROSE, followed by 20× dialysis in PBSovernight. Ztnf4-specific antibodies were characterized by an ELISAtiter check using 1 μg/ml of the appropriate peptide antigen orrecombinant full-length protein (hurtnf4s-NF-Bv) as antibody targets.The lower limit of detection (LLD) of the rabbit anti-hurtnf4-1 affinitypurified antibody on its specific antigen (hurtnf4-1 peptide, SEQ IDNO:59) is a dilution of 5 ng/ml. The lower limit of detection (LLD) ofthe rabbit anti-hurtnf4-2 affinity purified antibody on its specificantigen (hurtnf4-2 peptide, SEQ ID NO:60) is a dilution of 0.5 ng/ml.The lower limit of detection (LLD) of the rabbit anti-hurtnf4-2 affinitypurified antibody on the recombinant protein hurtnf4s-NF-Bv is adilution of 5 ng/ml.

Monoclonal antibodies were generated and selected for inhibition ofinhibition of biotin-labeled soluble ztnf4. None of the TACI monoclonalantibodies (248.14, 248.23, 248.24, or 246.3) block ztnf4 binding onBCMA. Monoclonal 248.23 reduces binding of 10 ng/ml ztnf4-biotin toabout 50% when conditioned media is diluted to 1:243 and reduces bindingto about 2× in undiluted media. Monoclonal 246.3 reduces binding of 10ng/ml ztnf4-biotin to about 50% between a 1:243 and 1:181 dilution ofconditioned media and reduces binding 5× in undiluted media.

Example 19 Ztnf4 Levels in SLE Patients

Levels of ztnf4 in the SLE patients, relative to normal individuals, wasdetermined using an ORIGIN ASSAY as described above. A standard curveprepared from soluble, human ztnf4 at 10 ng/ml, 1 ng/ml, 0.1 ng/ml, 0.01ng/ml and 0 ng/ml was prepared in ORIGIN buffer (Igen). All patientsamples were run in triplicate, 25 μl of final volume. The standards andsamples were incubated at room temperature for 2 hours with a captureantibody, biotinylated rabbit anti-human ztnf4-NF BV polyclonalantibody, diluted to 1 μg/ml in Origin Assay Buffer (IGEN) and adetection antibody, ruthenylated rabbit anti-human ztnf4-NF BVpolyclonal antibody, diluted to 1 μg/ml in Origin Assay Buffer (IGEN).Following the incubation the samples were vortexed and 0.4 mg/mlstreptavidin Dynabeads (Dynal) were added to each of the standards andsamples at 50 μl/tube and incubated for 30 minutes at room temperature.Samples were then vortexed and using an Origin 1.5 Analyzer (Igen)according to manufacturer's instructions.

Elevated levels of ztnf4 were seen in the serum of patients diagnosedwith SLE as compared with normal control serum donors (FIG. 10). Twentyeight normal control samples were tested and samples from 20 patientsdiagnosed with SLE. The data is reported as fold increase of ztnf4levels in the patient or control samples as compared to an arbitraryhuman reference serum sample. The average of the 28 control samples was1.36 fold over the human reference sample and the average of the 20 SLEpatient samples was 4.92. Seven out of the 20 SLE patients had ztnf4levels that were two fold over the average of the control samples,whereas there was only one control individual that had a greater thantwo fold level over the control average.

Example 20 TACI-Ig and EAMG Mouse Model

The effect of TACI-Ig is determined by administering TACI-Ig duringongoing clinical myasthenia gravis (MG) in B6 mice. One hundred B6 miceare immunized with 20 μg acetylcholine receptor (AChR) in completeFreunds Adjuvant (CFA) on days 0 and 30. Approximately 40-60% of micewill develop moderate (grade 2) to severe (grade 3) clinical MG afterthe boost with AChR. Mice with grade 2 and 3 clinical disease aredivided into three groups (with equal grades of weakness) and weighed(mice with weakness also lose weight, since they have difficulty inconsuming food and water) and bled for serum (for pre-treatmentanti-AChR antibody and isotype level). Group A is injected I.P with PBS,group B is injected I.P with murine IgG2a-FC as a control protein (100μg), and group C is injected with 100 μg of murine TACI-IgG2a-FC threetimes a week for 4 weeks. Mice are screened for clinical muscle weaknesstwice a week and weighed and bled for serum 15 and 30 days after thecommencement of treatment. Whole blood is collected on day 15 todetermine T/B cell ratio by FACS analysis using markers B220 and CD5.Surviving mice are killed 30-45 days after the initiation of treatment,and their carcasses are frozen for later extraction of muscle AChR (Wuet al. Protocols in Immunology. Vol. 3, Eds. Coligen, Kruisbeak,Margulies, Shevach, and Strober. John Wiley and Sons, New York, p.15.8.1, 1997) to determine the loss of muscle AChR, the primarypathology in MG.

Dose Response Study

Serum antibodies to mouse muscle AChR is determined by an establishedradioimmunoassay, and anti-AChR antibody isotypes (IgM, IgG1, IgG2b andIgG2c) is measured by ELISA. Such methods are known, see for example, Wuet al. ibid. The effect of TACI-Ig on ongoing clinical MG, anti-AChRantibody and isotype level, and muscle AChR loss is determined.

Approximately 100 mice will each be immunized with 20 μg AChR in CFA onday 0 and 30. Mice with clinical MG are divided into 4 groups. Group Ais injected I.P with 100 μg control FC (murine IgG2a-FC), group B isinjected with 20 μg control FC (murine IgG2a-FC), and group C isinjected 100 μg murine TACI-IgG2a-FC, and group D is injected with 20 μgmurine TACI-IgG2a-FC three times a week for 4 weeks. Mice are weighedand bled for serum before and 15 and 30 days after the start of thetreatment. Serum is tested for anti-AChR antibody and isotypes as above.Muscle AChR loss will also be measured.

From the foregoing, it will be appreciated that, although specificembodiments of the invention have been described herein for purposes ofillustration, various modifications may be made without deviating fromthe spirit and scope of the invention. Accordingly, the invention is notlimited except as by the appended claims.

1. A method of inhibiting B lymphocyte proliferation in a mammal,comprising administering to the mammal a composition comprising a fusionprotein that consists of a first portion and a second portion, whereinthe first portion and the second portion are joined by a peptide bond,wherein the first portion of the fusion protein consists of the aminoacid sequence of amino acid residues 25 to 104 of SEQ ID NO:6 whereinthe second portion of the fusion protein is an immunoglobulin heavychain constant region and wherein the fusion protein binds ztnf4.
 2. Themethod of claim 1, wherein the immunoglobulin heavy chain constantregion is a human immunoglobulin heavy chain constant region.
 3. Themethod of claim 2, wherein the human immunoglobulin heavy chain constantregion is a human immunoglobulin heavy chain constant region of IgG1. 4.The method of claim 1, wherein the composition comprises multimericproteins comprising one or more polypeptide fusions.
 5. The method ofclaim 4, wherein the composition comprises dimeric proteins comprisingone or more polypeptide fusions.
 6. The method of claim 1, wherein saidB lymphocyte proliferation is associated with an autoimmune disease. 7.The method of claim 6, wherein said autoimmune disease is systemic lupuserythematosus, myasthenia gravis, multiple sclerosis or rheumatoidarthritis.
 8. The method of claim 1, wherein said B lymphocyteproliferation is associated with bronchitis, emphysema or end stagerenal failure.
 9. The method of claim 1, wherein said B lymphocyteproliferation is associated with renal disease.
 10. The method of claim9, wherein said renal disease is glomerulonephritis, vasculitis,nephritis or pyelonephritis.
 11. The method of claim 1, wherein said Blymphocyte proliferation is associated with renal neoplasms, multiplemyelomas, lymphomas, light chain neuropathy or amyloidosis.
 12. Themethod of claim 1, wherein said inhibiting B lymphocyte proliferation isassociated with regulation of immune response.
 13. The method of claim1, wherein said inhibiting B lymphocyte proliferation is associated withimmunosuppression.
 14. The method of claim 13, wherein saidimmunosuppression is associated with graft rejection, graft versus hostdisease, autoimmune disease or inflammation.
 15. The method of claim 14,wherein said autoimmune disease is insulin dependent diabetes mellitusor Crohn's Disease.
 16. The method of claim 14, wherein saidinflammation is associated with joint pain, swelling, anemia or septicshock.